The Lexington-class: America's Only Battlecruisers

      Of the major naval powers at the end of WWI the U.S was the only power not to have built battlecruisers. The British pioneered the concept in 1907 with the HMS Invincible and were quickly followed by the Germans with the SMS Von der Tann. At the beginning of the 20th century it was a recognized deficiency within the U.S. Navy that there were not enough cruisers to scout and support the main battle line. Beginning in the early 1910s the General Board began to develop designs for what a U.S. battlecruiser should look like. In 1916 Congress granted funding for a class of six battlecruisers, but due to WWI construction did not start until 1920 after the U.S. entry into WWI and a major redesign of the class using British experience from Jutland. Unfortunately, or perhaps fortunately, the Lexington-class was one of the classes of ships scraped after the ratification of the Washington Naval Treaty. Of the six ships planned only two were completed (both as aircraft carriers), the Lexington and Saratoga of WWII fame. However, the focus of this post is on the Lexington-class in it's original battlecruiser form.
      In the early 1900s the General Board wanted to enlarge the U.S. cruiser fleet to provide scouts for the battle line of the Navy. Congress was unwilling to provide funds for the requested cruisers, rather focusing on battleships. This forced destroyers to take up the slack in acting as the eyes of the U.S. battle line. In 1916 Congress finally gave it's approval for a class of six battlecruisers to be completed by 1920. This first design approved by Congress was to be armed with 10 14in guns, a displacement around 33,500 tons (this first design is comparable to the British Renown), a top speed of 35 knots, and very thin armor. Work was ceased on the design with the American entry into WWI  in November 1917 as all shipyard capacity was devoted to merchant vessels and ASW craft. With the U.S. entry into WWI Britain gave the U.S. access to their experience with battlecruisers, especially that gained from Jutland. The two redesigns of the Lexington-class from 1917 until 1919 turned the Lexington-class into what was essentially a fast battleship, combining the speed of a battlecruiser with the firepower of a battleship. Armament was increased to 8 16in guns, armor was increased which resulted in a drop in the class's top speed to 33 knots. This redesign was heavily influenced by the HMS Hood which the British viewed as a hybrid battleship and battlecruiser.
     The final design specifications of the Lexington-class are drawn from Norman Friedman's U.S. Cruisers: An Illustrated Design History and Siegfried Breyer's Battleships and Battlecruisers, 1905 to 1970.

Displacement
Light ship	43,500
Deep load	44,938
Dimensions
Length (waterline)	850 feet
Length (overall)	874 feet
Beam	105 feet
Draft (light ship)	30 feet
Armament
Main battery	8 16”/50 Mark 2 guns
Secondary battery	16 6”/53 Mark 13 guns
Anti-Aircraft battery	6 3”/50 Mark 10 guns
Torpedo Tubes	8 21” Tubes
Armor
Main side belt	7” tapering to 5” at the ends of the ship
Upper deck	1.25” to 2.25”
Upper armored deck	1.5”
Lower armored deck	2”
Machinery
Shaft horsepower	180,000 SHP
Maximum speed	33.25 knots
Endurance @ 10 knots	10,000 miles

16"/50 Mark 2 outside the Washington Naval Yard in 1974

     The Lexington-class battlecruisers were to carry a main armament of eight 16"/50 Mark 2 guns in four twin turrets. Originally the Lexingtons were to be armed with 14 inch guns, but were upgunned due to the increasing caliber of naval guns worldwide and the longer range and better penetration of 16" guns. The Lexingtons were also to carry 16 6"/53 guns (10 in casemates and 4 in open air) to defend against destroyers. The anti-air armament consisted of 4 3"/50 guns at the time of the design, but by the time the ships were being built the number was upped to 8. Had the Lexingtons been built as planned it is likely that their casemate guns would have been removed and replaced at some point, and the guns mounted in the open would have been removed in the 1930s to make room for an increased AA armament. Their AA armament would have also been exponentially increased with everything from 0.50" MGs in the 30s to twin 5"/38 guns and 40mm Bofors cannons by WWII. To get an idea of the layout of the armament to be carried by the Lexington-class below is a sketch produced by the General Board in 1919 which was one of the later designs and extremely similar to the final design (I know there is an actual line drawing of the Lexingtons produced by the General Board in June of 1919, but the Navy does not seem to have it in their online archives).

(Click on the photo to enlarge)

     The armor scheme on the Lexingtons was influenced by the HMS Hood in that the main side belt was inclined outwards at 11.5 degrees to increase it's effective thickness against horizontal fire. The main side belt was to have a maximum thickness of 7 inches tapering to 5 inches at the ends of the ship. The cumulative deck protection was 3.75 inches split between the main deck, the protective deck, and the splinter deck. Turret armor was 11in on the face, 6in on the sides, and 5in on the roof of the turret. Comparatively, the Hood had a main side belt of 8in which thinned to 5-6in at the ends of the ship. Deck armor was 3in amidships, and 7in over the magazines.
     The top speed of the Lexington-class as designed was to be 33 knots. The Lexingtons would have had 16 Babcock boilers powering 4 GE turbines, each turbine driving one of four propellers. Total shaft horsepower of each Lexington was to be 180,000 SHP. This powerful machinery would later prove invaluable during the Lexington and Saratoga's days as carriers. To compare against a contemporary battlecruiser, the Hood had a top speed of 31 knots during trials, and that achieved by pushing her boilers beyond design specifications (the design SHP of the Hood was 144,000 but the speed of 31 knots was achieved with 151,280 SHP).
     While the Lexington-class was the only class of battlecruisers built (not commissioned) by the U.S. Navy, the Alaska-class have also been referred to as battecruisers in the last few decades in various books. However, the Lexington-class was designed explicitly to act as scouts for the main battle line of the Navy and to act as a fast squadron as part of the battle line itself. The Alaska-class was designed as a "cruiser-killer" meant to take on Japanese heavy cruisers, and escort carriers on operations independent of the Battle Force without detracting from the firepower of the Battle Force. The design requirements were different for the Lexingtons and the Alaskas. The Lexingtons were faster, better armored (relative to the Alaskas), and better armed than the Alaskas to carry out their mission of supporting the battle line. Whereas, the Alaskas were meant to operate apart from the Battle Line supporting carrier operations. Any comparison between the two class is wrong because they were designed for different mission sets.

Post-War Yamato-class Turret Armor Tests

     THAT is a section of turret armor plating that was slated to be fitted aboard the IJN Shinano. As the Shinano was converted to an aircraft carrier, the turret armor was never fitted. The test was conducted in October 1946, with a 16/50 Mark 7 gun firing a super heavy AP shell. The tests were conducted at point-blank range. Had the armor been inclined back at the 45 degrees as planned, it would have been impenetrable to guns of any caliber at any range, bar point blank. Read more over at the NavWeaps Technical board.

Alaska-class CBs: America's Cruiser-Killers

     The United States Navy has never officially completed any ships under the designation "battlecruiser". There was a class of battlecruiser constructed during the early 1920, the Lexington-class, but none were completed as battlecruisers (two were completed as aircraft carriers). However, during WWII the U.S. commissioned two vessels known as the Alaska and Guam. They were designated "large cruisers", but had some characteristics of battlecruisers. This post will cover the mission for which the Alaskas were designed, their specifications, armament, armor scheme, propulsion, and their operational history.
     At the time the Alaska-class was designed, the Japanese heavy cruisers were becoming a threat to any then-future carrier operations independent from the Battle Force. At the same time, Germany was building the Duetschland-class "pocket battleships" for commerce raiding. France was also rumored to be developing a class of 17,500 ton commerce raiders carrying 12in guns. Thus, a class of ships was needed to be able to escort carriers, and defend the carriers without detracting from the firepower of the Battle Force. At, the same time this class would have to be able to hunt down and kill enemy commerce raiders. This is the niche that was to be filled by the Alaska-class.
      Final design specifications of the Alaska-class are drawn from William Garzke's Battleships: United States Battleships, 1935-1992:

Armor
light ship	25,971 tons
standard	27,000 tons
full load	34,253 tons
Dimensions
length overall	808’ 6” (246.431m)
waterline length	791” 6” (241.249m)
maximum beam	90’ 9.375” (27.670m)
maximum draft	31’ 9.25” (9.684m)
Armament
main battery	9 - 12”/50 (305mm)
secondary	12 - 5”/38 (127mm)
antiaircraft	56 - 40mm/56
	34 - 20mm/76
Armor
main side belt	9.0” tapered to 5.0”, inclined 10 degrees (229mm-127mm)
main deck	1.40” (34mm)
second deck centerline	2.80” + 1.0” (71mm + 25mm)
third deck	0.625” (16mm)
Machinery
shaft horsepower	150,000
maximum speed	33 knots
endurance @ 15 knots	12,000nm

     Armament. The Alaska-class was the last class of ship in the U.S. Navy to carry 12in guns, and probably the last in the world. However, the guns that the Alaskas were equipped with actually outclassed the 14"/45 Marks 1, 2, 3 and 5 guns carried by the New York-class and Pennsylvania-class battleships early in their careers. Specifically the guns carried by the Alaskas had better penetration capabilities than the earlier 14in guns at all ranges*. This was achieved by the use of the Mark 18 "super-heavy" AP shell which weighed in at 1,140lbs (517kg). The main battery turret armor was 325mm on the face, 152-133mm on the sides, and 127mm on the roof. The secondary armament consisted of 12 5"/38 guns in 6 twin mounts. Antiaircraft armament consisted of 56 40mm/56 cannons in 14 quad mounts, and 34 20mm/76 cannons in single mounts.  The massive secondary and anti-aircraft armament carried on the Alaska-class made them immensely valuable for kamikaze defense late in WWII. Had the Alaskas been kept in service after WWII, it is likely their 20mm cannons would have been removed entirely, and their 40mm mounts replaced by the then-new 3"/50 Mark 27 guns.

The Guam in Pearl Harbor in February 1945

     Armor. Armor was as listed above in the specifications. Additional armor numbers are, 280 to 330mm for the barbettes, and 270 mm on the control tower. As to underwater protection, it was almost nonexistent on the Alaska-class. Rather, the Alaskas relied on internal subdivision as protection against torpedo and underwater shell damage.  

      Propulsion. The Alaska-class ships were driven by four sets of General Electric geared turbines. The turbines were driven by eight Babcock & Wilcox Express boilers. The max steam pressure for the boilers was 45kg per square cm. The turbines drove four propellers. Top speed as designed was 33 knots, but the trials showed a top speed of 32.72 knots. Electricity was provided by four generators. Each engine room (there were two) had a single General Electric turbo-generator rested at 1,000kW, 450V AC. At either end of the propulsion spaces were single GE generators each rated at 1,062kW, 450V AC.
      The Alaska-class did suffer from a number of problems. The Alaska-class lacked sufficient space for a CIC, making conditions extremely crowded. The Alaska-class also had relatively thin armor for her displacement, at a time when it was possible to give ships a high speed even with thick armor (see the Iowa-class). The top speed of 32.72 knots achieved during trials lower than what was predicted or designed. Finally, underwater protection aboard the Alaskas was nonexistent. Any conventional side protection scheme was sacrificed to reach higher speeds, and would have left the Alaskas vulnerable to torpedo attack had the Alaska entered the war earlier than they did. This with a displacement approaching that of battleships.
      History. Construction of the Alaska-class was authorized by the Two-Ocean Navy Act in 1940. Six vessels were authorized, of which two were completed, three were cancelled, and one was scrapped before being commissioned. The two vessels that were completed were the Alaska and Guam. The Alaska was laid down on 17 December 1941, and commissioned 17 June 1944. The Guam was laid down on 2 February 1942, and commissioned on 17 September 1944. The third vessel which was constructed, was the Hawaii. She was launched, but never completed (more on the Hawaii later).
        Operational History. The Alaskas both had very short careers. The Alaska first screened aircraft carriers attacking the Japanese Home Islands in March 1945, and destroyed two Japanese aircraft on 18 March. She then participated in shore bombardment of Minami Daito Jima on 27 March, and in late July took part in sweeps of the East China Sea. After the Japanese surrender the Alaska supported minesweeping operations along the Chinese coats, supported Army landings at Inchon on 8 September,  and sailed to Tsingtao to hold the port by force until Marines arrived to take over.  The Guam arrived at Pearl Harbor on 8 February 1945, and sailed for Ulithi on 13 March joining the Alaska. From there the Guam escorted TF 58 on a raid of the Japanese Home Islands, breaking off on 19 March to escort the USS Franklin back to Ulithi. On 27 March the Guam participated in a bombardment of Okinawa. From the Invasion of Okinawa to the end of the war, the Guam participated in a series of raids in the east China Sea and the Chinese coast. After the end of the war the Guam showed the flag along the Chinese coast, and participated in the occupation of Korea.

The Hawaii just prior to the suspension of her construction.

      The Hawaii. The Hawaii was never completed, and she was scrapped in 1959. However, before her scrapping there were two proposals to convert her. One proposal was a conversion to a command ship similar to the Northampton, but larger. This proposal was nixed when it was shown that an escort carrier, the Wright, could the same thing for cheaper. The second proposal was a conversion to a guided missile cruiser, carrying an ASROC launcher, twin Talos SAM launchers, and twin Tartar SAM launchers. Other variants of the missile proposal included fitting the Hawaii with 12 U.S.-built V-2 missiles, or later 20 Polaris ICBMs. In the end the missile proposal was scrapped as being too costly.
      The Alaska-class cruisers were neither battlecruisers or battleships, regardless of their appearance. They were designed from the beginning as a counter to perceived threats from hostile cruisers. Their main armament was meant not for slugging it out with enemy battlewagons (though it is possible the 12/50 Mark 7 may have been better than the 14" guns carried by the Kongo-class battlecruisers), it was meant to overwhelm an enemy heavy cruiser. The mission the Alaskas were designed was by 1944, non-existent, and in hindsight they were unnecessary. They were anachronisms born from the lifting of the Washington Treaty restrictions on cruisers. Regardless of that fact, they served well and were not inherently bad ships.
   


*Unfortunately, I cannot link directly to penetration tables for the 12in/50 and 14in/45 guns. If you wish to compare the penetrations for the guns, the requisite tables are on the NavWeaps pages for each gun.  The NavWeaps pages are linked to in the post.

Scharnhorst and Gneisenau: Germany's Last Battlecruisers

     The Scharnhorst-class was a class of battleships or battlecruisers, depending on one's definition, produced by Nazi Germany during the 1930s immediately before WWII. They were meant to serve as a counter to the French Dunkerque-class which was being be built around that time. Built to fight in the North Sea, their armament was limited by the political need not to anger Britain or France. The Treaty of Versailles in 1919 banned Germany from building new battleships, but allowed "armored vessels". However, the Anglo-German Naval Agreement (AGNA) allowed Germany 35% of the total tonnage of the Royal Navy, and new battleships or battlecruisers. This agreement would pave the way for the construction of the Bismarck-class and the H-class.

     Three days before the signing of the AGNA on 15 June 1935, the keel of the Scharnhorst was laid down in Wilhelmshaven. One month before the keel for the Gneisenau was laid down in Kiel on 16 May. The designs for these ships had been completed long before, with an armament of 9 28cm/54.5 SK C/34 guns in three triple turrets (one the few German ship classes to be equipped with tripe turrets) being selected. Armor consisted of a vertical 350mm belt tapering off to 170mm at the outboard slope of the armor deck, and deck armor ranging from 50mm to 105mm. The secondary armament consisted of 12 15cm/55 SK C/28 guns mounted in 4 twin and 4 single turrets (these are not be confused with the 150mm AA guns the Scharnhorst-class carried). The armor on the 28cm turrets was 360mm on the face, 200mm on the sides, 150mm on the roof, and a range of 350mm to 200mm on the barbettes*. Displacement was 37,100 tons. One interesting point about their armor is that generally on battleships, the armor corresponded to the main battery (e.g. guns of 406mm, armor of a thickness that would defeat a 406mm shell). This was not the case with the Scharnhorst-class which carried far more than necessary to defeat an 283mm shell.

     The Scharnhorst and Gneisenau were considered by the Kriegsmarine to be battleships, but were viewed by the Royal Navy as battlecruisers. Their armor listed above compares very favorably to Britain largest battlecruiser, the HMS Hood. The Hood had a 305mm belt (the belt on the Hood was angled at 12 degrees, whereas the Scharnhorst-class had vertical belts), which tapered off to 127mm and 152mm at the ends of the ship. Turret armor on the Hood was slightly heavier than the Scharnhorst-class, the face of the Hood's turrets was 373mm, 299 to 274mm on the sides, and 124mm on the roof. 

     The Scharnhorst and Gneisenau were built for combat in the North Sea against French battleships which is why they carried battlecruiser thickness armor. The 28cm guns were selected for their high rate of fire and the fact that the Dunkerque-class was thought to mostly lightly armored. However, when faced with vessels with a greater armament and armor the Scharnhorst and Gneisenau were unable to return any meaningful damage.

     The operational history is the Scharnhorst-class is excellent with both ships serving well throughout their service lives. During the Invasion of Norway the Scharnhorst and Gneisenau sank the carrier HMS Glorious and two escorting destroyers. During this engagement the Scharnhorst was hit by one torpedo launched by one escorting destroyers which did serious damage to propulsion and flooded four watertight compartments. From the sinking of the Glorious for about six month the Scharnhorst and Gneisenau were inactive while the Scharnhorst underwent repairs. In January of 1941 both ships sortied from Kiel to attack British convoys. They escaped detection and came upon the convoy HX 106 which was escorted by the HMS Ramilles, causing the Scharnhorst and Gneisenau to break off their attack. The ships returned to Brest where, after undergoing repairs, participated in the infamous Channel Dash in February 1941.  Both the Scharnhorst and Gneisenau sustained mine damage off Holland during the Channel Dash and were forced to undergo repairs in Kiel. From February 1941 to March 1941 the Scharnhorst and Gneisenau would remain in German waters. In March 1943 the Scharnhorst was deployed to Norway where she was to link up with the Tirpitz and attack convoys sailing to Russia. The Gneisenau was also supposed to sail with her, but took heavy bomb damage from RAF bombers in late February 1942, and was slated to be reconstructed. This reconstruction would have included an upgrade to her armament with 6 380mm guns similar to those carried on the Bismarck-class. From here the ships separated. 

     The Scharnhorst arrived in Norway on March 22nd. From April 1943 to September 1943 the Scharnhorst and Tirpitz were inactive due to a fuel shortage. Then on September 8th the Scharnhorst and Tirpitz sortied to Spitzbergen where they bombarded shore installations. On December 22nd the Scharnhorst sortied for her final mission (the Tirpitz did not sail with her because she had been damaged by British midget submarines soon after the Spitzbergen operation) to attack convoy JW 55B. 

     Convoy JW 55B was escorted by three British cruisers, the light cruisers Sheffield and Belfast as well as the heavy cruiser Norfolk (these were known as Force 1). The King George V-class battleship Duke of York was also in the area providing overwatch for JW 55B and another convoy, RA 55A. The Scharnhorst was unable to make contact with JW 55B, but did find the three escorting cruisers. Force 1 detected the Scharnhorst at a range of 33,000 meters from Force 1, 60,000 meters from the convoy. The Scharnhorst was unaware of the British presence since her radar was off to avoid detection. The British opened fire at a range of 8,600 with star shells to illuminate the Scharnhorst at 0840 on December 26th. During this encounter (from 0925 to 0955) the Scharnhorst sustained two 203mm hits, one of which destroyed the forward rangefinders and crippled the Scharhorst's radar capability (the shell sheared off the radar antenna and killed all personnel in the radar receiving room). The Scharnhorst was now blind in the forward sector, as the aft radar had a limited sweep over the forward sector. At 0955 the Scharnhorst was able to break away from Force 1 and escape. 

"The sinking of Scharnhorst"

     At 1200 the Belfast was able to reestablish radar contact with the Scharnhorst. From this point till about 1315 the Scharnhorst fought with Force 1, scoring a serious hit on the Norfolk around 1223. Around 1315  broke contact and made for Norway. However, in making for Norway the Scharnhorst had to cross the course of the Duke of York. At 1617 the Duke of York made radar contact with the Scharnhorst at a range of 42,500 meters. At 1650 the Duke of York opened fire on the Scharnhorst after she had been illuminated by star shells from the Belfast.  

Map of the Battle of North Cape (click to enlarge)

     This began the last surface engagement of German and British capital ships of WWII. The duel that began was highly unequal because the Scharnhorst 283mm guns simply could not penetrate the Duke of York's armor at any point. The Scharnhorst was able to  damage the Duke of York's superstructure, and temporarily knock out her fire control radar. However, between 1650 and 1842, when the Duke of York ceased firing, the Scharnhorst took at least 13 356mm hits. At the end of the gunnery duel the Scharnhorst was still making around 22 knots, leading to a British torpedo attack around 1850. 4 torpedoes hit, slowing the Scharnhorst to 12 knots, though the chief engineer reported he could still produce 22 knots. At this point a second torpedo attack was made because of the apparent inability to sink German capital ships by gunfire (this was learned from inability to sink the Bismarck by gunfire). At 1900 all confidential papers were burned by order of the Scharnhorst's captain. At 1945 the Scharnhorst sank bow first with her propellers still turning. Out of a crew of 1968 officers and enlisted man, only 36 enlisted men survived the engagement. Thus, ended the Battle of North Cape.

     As to the fate of the Gneisenau, work was eventually stopped in early 1943 at the order of Hitler, who was angry at the failure of German surface raiders. The 283mm turrets that had been removed to make way for the new 380mm turrets, were shipped to Norway. There they were installed as coastal defense guns, where one remains there to this day. From 1943 to till 1945 nothing happened to the remains of the Gneisenau. In March 1945 the Gneisenau was towed into the entrance of the harbor of Gotenahfen where she was sunk as a block ship to delay the Advance of the Red Army. Her hull was scraped by the Polish government from 1947 to 1951.

        The Scharnhorst-class was never able to fulfill it's mission of fighting in the French or British in the North Sea. They were forced into a commerce raiding role which they were not optimized for, and when faced with superior opponents were unable to deal damage back. Their armor was excellent for their displacement, but they did not have the survivability of German WWI battlecruisers. Germany packed a lot of punch into relatively small hulls, an they would have performed well in a hypothetical North Sea engagement. However, when forced into a commerce raiding role or engaging more heavily armored ships, they simply could not do the job.

* All turret armor numbers are taken from Naval Weapons of World War Two by John Campbell.

Flashback Friday: O-class Battlecruisers

     Part of Plan Z was the construction of three O-class battlecruisers. The design originated from a proposal to increase the armament of the proposed P-class to 380mm guns.The O-class was designed for commerce raiding and their specifications show this. By mid-1939 all work on the P-class had stopped and was redirected into the O-class. 

     O-class specifications*:

Displacement                       31,142 tons

Full load displacement          35,367 tons

Waterline length                    246.0m

Waterline beam                     30.0m

Draft (design)                        8.0m

Draft (full load)                      8.8m

Armament                              six 38cm/52 SK C/34 paired

                                             six 15cm/48 Tbts KC/36T paired 

                                             eight 10.5cm/65 SK C/33 paired (AA)

                                             eight 3.7cm/L83 SK C/30 paired (AA)

                                             twenty 2cm/65 C/30 in five quads (AA)

                                             twelve 533mm torpedo tupes in four fixed triple mounts

                                             four Arado-196 floatplanes

         

Speed                                  33.5 knots at designed displacement

Shaft horsepower                 176,000

Endurance                           14,000 nautical miles at 19 knots

Protection                            90mm upper belt

                                            190mm  main side belt

                                            30 mm upper deck

                                            60mm armor deck

     Let's start with protection. In comparison to the numbers listed above for the O-class, the HMS Hood had a a side belt of 203mm, a 127mm upper belt, an upper deck of 32mm, and a lower deck of 48mm. The O-class had lighter armor than the Hood. On 24 May 1941 the Hood was sunk by a single hit from the Bismarck which penetrated to her magazines, which detonated. The loss of the Hood directly confirmed the insanity of lightly armored capital ships engaging hostile capitals ships. The protection scheme of the O-class was obsolete the second it was designed. The lack of armor may have saved weight, leading to a greater speed, but the cost in staying power was tremendous. For further examples of lightly armored battlecruisers being lost to magazine explosions, look no further than the Indefatigable, Queen Mary and Invincible. All lost to magazine explosions at Jutland. The O-class would have been dead the moment it engaged a battleship.

The explosion of the Queen Mary at Jutland

     Moving on to the armament, this is a spot where the O-class wasn't as bad. The O-class was armed with 6 38cm guns. Though while this armament would have been excellent for sinking merchant vessels, in an engagement with hostile battleships the O-class would have been heavily outgunned. However, the O-class had the advantage in speed over almost every class of battleship that served in WWII (the Iowa-class being the exception). Assuming a hostile battlecrusier had been able to catch an O-class, the gunnery duel would have been almost equal. For comparison the Repulse-class battlecruisers carried six BL 15in MK 1 guns, and the French battleship Dunkerque carried 8 330mm guns. As to the secondary anti-aircraft armament, the O-class would have had very light defenses against air attacks. Only 36 guns of varying calibers. This was light even for German vessels. The Bismarck carried 16 10.5cm AA guns, 16 3.7cm guns, and 20 2cm guns in comparison. 

The Tirpitz firing her main battery

     The power plant for the O-class were eight 24 cylinder MAN diesel engines (V type), arranged four to a shaft. The diesels generated 13750 horsepower each continuously, and had a maximum rating of 15000 horsepower each. The centerline shaft (the O-class would have had three propellers) was driven by a steam turbine and four high temperature and pressure boilers. The operating temperature for the boilers would have been 460 degrees celsius (and could be superheated to 960 degrees celsius), and the operating pressure would have been 55kg per square cm. The steam plant was rated at 55,000 horsepower normally, and 60,000 at maximum. The use of mixture of diesel-steam powerplant allowed a relatively low fuel consumption rate, and an endurance of 14,000nm to 15,000nm at 19 knots. Though, this range would only have been attained with only the diesels in operation. 

     The method in which these ships were to be used, was commerce raiding. It was planned that a task force made up of 3 H-class battleships, an aircraft carrier, with cruisers and destroyer as escorts, would engage convoy escorts. Allowing the battlecruisers to strike the undefended merchant vessels. How this proposed task force would break out of the North Sea, or the English Channel has not been shown. Had such a force attempted a breakout, the British would have undoubtedly sortied the Home Fleet to engage the force. Any O-class vessel attached would have almost assuredly been lost in an such an engagement. It must be remembered that the British were able to keep the Geramn High Seas Fleet bottled up in the North Sea for the duration of WWI. The location of Germany would have precluded the effective use of an O-class battlecruiser as a commerce raider simply because of the gauntlet that would have had to be run to reach the British convoys.

     The O-class is an interesting mental exercise, in what a Bismarck with no armor would look like. However, in combat the glaring lack of armor would have doomed them to penetrating hits to magazine and machinery spaces. The armament was passable, but lacking in the AA role. The mission that was planned for the O-class was, while feasible, do not take into account the location of Germany or the possibility of an encounter with better armored and/or armed opposition. The O-class as designed was a floating coffin, nothing more, nothing less.

*Garzke, William and Dulin, Robert. Battleships: Axis and Neutral Battleships in WWII.

Painting at top by Richard Allison.

Flashback Fridays: H-Series Battleships

     This week's Flashback Friday focuses on Nazi Germany's H-series battleships. The H-series was a series of battleship proposals put forth by the Third Reich for Plan Z. Of 5 H-series proposals, only one class made it to construction, the H-39. The other classes were the H-41, H-42, H-43 and the titanic H-44. Plan Z called for six H-39 battleships, of which construction began on two, the other four never made it to construction. Both H-39s were scrapped in November 1941. It would take several paragraphs to explain the specifications on all five H-series proposals, so below is a table of specs from German Warships: 1815-1945:

Design	H-39	H-41	H-42	H-43	H-44
Displacement	56,444 t (55,553 long tons)	68,800 t (67,700 long tons)	90,000 t (89,000 long tons)	111,000 t (109,000 long tons)	131,000 t (129,000 long tons)
Length	277.8 m (911 ft 5 in)	282 m (925 ft 2 in)	305 m (1,000 ft 8 in)	330 m (1,082 ft 8 in)	345 m (1,131 ft 11 in)
Beam	37 m (121 ft 5 in)	39 m (127 ft 11 in)	42.8 m (140 ft 5 in)	48 m (157 ft 6 in)	51.5 m (169 ft 0 in)
Draft	10 m (32 ft 10 in)	11.1 m (36 ft 5 in)	11.8 m (38 ft 9 in)	12 m (39 ft 4 in)	12.7 m (41 ft 8 in)
Main	8 × 40.6 cm (16.0 in)	8 × 42 cm (17 in)	8 × 48 cm (19 in)	8 × 48 cm (19 in)	8 × 50.8 cm (20.0 in)
Secondary	12 × 15 cm (5.9 in) and 16 × 10.5 cm (4.1 in)	12 × 15 cm (5.9 in) and 16 × 10.5 cm (4.1 in)	12 × 15 cm (5.9 in) and 16 × 10.5 cm (4.1 in)	12 × 15 cm (5.9 in) and 16 × 10.5 cm (4.1 in)	12 × 15 cm (5.9 in) and 16 × 10.5 cm (4.1 in)
AA	16 × 3.7 cm (1.5 in) and 12 × 2 cm (0.79 in)	32 × 3.7 cm (1.5 in) and 12 × 2 cm (0.79 in)	28 × 3.7 cm (1.5 in) and 40 × 2 cm (0.79 in)	28 × 3.7 cm (1.5 in) and 40 × 2 cm (0.79 in)	28 × 3.7 cm (1.5 in) and 40 × 2 cm (0.79 in)
Torpedoes	6 × 53.3 cm (21.0 in)	6 × 53.3 cm (21.0 in)	6 × 53.3 cm (21.0 in)	6 × 53.3 cm (21.0 in)	6 × 53.3 cm (21.0 in)

      Several things stand out from the specs of the H-series, as the war went on (the H-41 through H-44 were designed from 1940-1942) AA armament increased in the designs, as evidenced by the increasing numbers of 37mm and 20mm cannons. The draft of the H-series also increased, to the point where the H-42, H-43, and H-44 would have been unable to use any German port without being dredged. Also, the main armament of the H-44 would have been 8 508mm guns which would have been the largest naval guns ever put to sea, larger than even Japan's Type 94 gun. It's also probable that the torpedo tubes would have been removed by the time any H-series battleship made it to construction.

       The H-39 was expected to fight at relatively close ranges, and as such was designed with vertical side belt armor, the upper side belt being 145mm, the lower side belt 220mm thick. It was calculated* that an H-39 would have been immune to a 16"/45 shell from 11km to 21km on the lower side belt, though a 16'/45 shell would have been able to penetrate the upper side belt at any distance. Deck armor ranged from 50mm-150mm depending on the area, magazines having the thickest deck armor, and machinery spaces having the thinnest armor. Turret armor ranged from 130mm-385mm thick, barbette armor ranged from 365mm to 240mm thick, with armor on the secondary battery being significantly thinner. The H-41 had increased armor on the deck, otherwise the armor scheme was the same as the H-39. Armor specs on the H-42 through H-44 are unavailable, but it would stand to reason that all three would have drastically increased armor in every area. 

      To get an idea of the size of the H-39 here is a photo where an depiction of an H-39 is superimposed next to the Tirpitz.

     The H-series battleships were for the most part hypothetical designs with the H-39 and H-41 being the most practical designs of the series. The designs after that, the H-42, -43, and -44, were all no more than mental exercises because by the time the designs were finished Germany was not in position to build anything larger than a destroyer for the duration of the war. In fact designs made after the H-41 were ordered by Hitler, and that can be seen in their massive size and armament. The H-39 and H-41 can be compared to the Montana-class in that they were practical designs, but the role they were meant to fulfill (slugging matches against other battleships) was taken over by aircraft and the materials slated for use in construction were diverted to more urgent needs. As to the H-42, -42, -44, they were no more than mental exercises along with the fact that they were huge, cumbersome, and impossible to build, similar to the Tillman Battleships.    

Photo Credit: Richard Allison

*Garzke, William H.; Dulin, Robert O. (1985). Battleships: Axis and Neutral Battleships in World War II. Annapolis: Naval Institute Press.