The III. Sqn henceforth comprised the Königs, plus Bayern, which was finally fully operational. She was joined in the fleet by her sister Baden early in 1917, which, once fully worked-up, replaced Friedrich der Große as fleet flagship on 14 March. Friedrich der Große then joined her sisters in the IV. Sqn, relieving Kaiser as its flagship. Baden was the penultimate big ship to join the fleet, the last being Hindenburg, which joined the I. SG in November, becoming its flagship on the 23rd.
The two Bayerns were the most highly developed of the German World War I battleships. Scuttled at Scapa Flow, Baden was raised in July 1919 and used as a target by the Royal Navy, largely to confirm the adequacy of the new generation of post-Jutland shells. These ships introduced the 15in gun to German service. Apparently they were conceived as a response to the British 13.5in gun rather than to the 15in, of which the Germans were unaware when the ships were designed. As in previous classes, the choice was a light, high-velocity shell: 750kg (1653lb) at 800 metres (2624 feet)/second. By way of contrast, the British 15in/42 fired a 1920lb shell at 2450 feet/second. The corresponding battlecruisers, which were never completed, were the Mackensen class, which would have been armed with 35cm (approximately 14in) guns, again to make it possible to build a fast battleship on about the same displacement as these ships. Although the light fast shell might seem intended for shorter ranges, these two ships had the long rangefinders (8m [26ft] base) introduced into the entire German fleet in wartime. Turret rangefinders were, unusually, near the face of each turret.
The Bayern Class
In June 1911, it was noted by the Navy Office that France was now following Great Britain and USA in going beyond 12in/305mm calibre by installing 340mm guns in its Bretagne class. In August, options studies began to consider 350mm, 380mm and 400mm guns, it having been at last agreed that Germany should consider leapfrogging existing big gun calibres, reversing previous preferences for lighter guns. A ceiling of 40cm was chosen because it was believed (wrongly) that British wire-wound gun technology could not support a larger calibre (an 18in [457mm] weapon successfully entered service with the Royal Navy in 1917).
Options were put forward for ships with ten 35cm or eight 40cm weapons, the Weapons Office preferring the heavier gun, as did the Construction Office on the basis that four turrets avoided the complexity added by a midships turret. This latter preference also led to studies into triple turrets to allow ten guns to be fitted in a four-turret arrangement.
In September 1911, the 28,250t eight-40cm scheme D1a was presented to the Emperor, with a 29,000t version developed in early January 1912, along with one of similar tonnage but ten 34.7cm. More work was done on the 40cm variant during the first half of 1912, but in spite of various attempts to cut costs, the ship proved unaffordable under the cash-limited 1913 programme, leading to a switch to the 38cm gun, the design for Battleship T (to be Bayern [ii]) and Ersatz-Wörth (Baden [ii]), being completed in September 1912 for ordering under the 1913 programme.
The armour of the new class was a further development of that of the Kaisers and Königs. While the lower edge of the midships belt now tapered to 170mm, it was now continued up to the main deck 250mm thick. The forward belt was heightened, although in compensation thinned to 75-150mm and terminated 15m short of the stem, where it was closed with a 140mm bulkhead. The aft belt extended to the main deck, 170–200mm, tapering to 120–150mm at the lower edge, closed with a 170mm bulkhead. The battery roof was thickened to 40mm, while the battery floor was now 25mm in thickness. The faces of the turrets were thickened to 350mm, with the roofs also increased in thickness. Barbettes were 350mm thick where not behind other armour, 250mm where screened by another barbette, 170mm behind battery armour, 80mm behind the upper belt and 25mm behind the main belt. The walls of the after conning tower were thinned to 170mm, to give scope for a 80mm roof.
The eight 38cm main guns were superimposed fore and aft in the same way as the contemporary British Queen Elizabeth and Royal Sovereign classes, the latter of which was also broadly comparable with the Bayerns as regards protection against gunfire. The secondary battery had two more guns than the Königs, and was to be on updated C/13 mountings, with higher elevation and thus longer range. Eight 8.8cm AA guns were originally envisaged, but (as in Lützow), both ships completed without any. Eventually, four were installed, around the after funnel in Bayern and a pair abreast each funnel in Baden. The torpedo battery was upgraded to the new 60cm torpedo, the enlarged compartment required, plus the ancillary air-flasks, causing the near-loss of Bayern when she was mined in 1917. Baden and Bayern both had their forward torpedo flat stripped and subdivided following mine damage to the latter in 1917, when its existence had threatened her survival.
Although it had been hoped (again) to install a COSAD propulsion system in the Bayerns, it was decided, given the delays in the diesel development programme, the first two ships should be given conventional three-shaft turbines. Nevertheless, as it was hoped that the diesel would be indeed be proven by the time that a third ship, the 1914 programme’s Ersatz-Kaiser Friedrich III (Sachsen [ii]), was ready to be engined, it was determined that she should receive a diesel. However, on 2 August 1914, it was decided that, in light of the outbreak of hostilities, such a course would be represent excessive risk, and that the future Sachsen should also receive all-turbine propulsion machinery (it was not until April 1917 that the big diesel designed for Prinzregent Luitpold finally passed its tests). On the other hand, Sachsen’s diesel was built and was inspected in the Germania erecting shop by the Naval Inter-Allied Control Commission in 1919.
To protect the top of the tall diesel, Sachsen’s protection was modified by the addition of a glacis over her after engine room, 140mm thick at the ends, 200mm at the sides and with a 80mm top. Otherwise, her protection was the same as that of the first pair, except for a uniform 200mm forward belt (150mm lower edge), extended to the stem with 30mm plating, with all barbettes 40mm behind the main belt; some of the midships deck was thickened to 50mm.
Early in the war the new threat of aircraft led to a progressive replacement of the four 8.8cm guns atop ships’ after superstructures by the same number of 8.8cm/45s on C/13 anti-aircraft mountings. The number of such guns was, however, reduced to two in certain of ships before the end of the war. Even though the Bayerns were designed with no fewer than eight 8.8cm AA guns, Bayern and Baden completed without any, and eventually mounted only four each, suggesting doubts as to their utility. On the other hand, the clear lack of utility of the low-angle 8.8cm weapons led to their progressive removal from operational ships, Derfflinger for example losing those under her bridge in 1915, and those around ‘C’ turret during her post-Jutland refit. The old ships of the II. Sqn had the forward pair of 8.8cm guns on the after superstructure replaced by 8.8cm/45 anti-aircraft weapons during the summer of 1916.
After Jutland, the elevation of main-battery guns was increased to reflect the experience of that battle, by lowering the trunnions of the guns, resulting in a higher elevation but lower depression. The battle had finally shown that the conception of short-range melee that had so long underpinned German capital ship armament policy had been a chimera, a realisation reflected in the upgunning of Ersatz-Yorck and the planning for 42cm armed ships for the future.