For the first half of the war, the principal armament on most U-boats was the 8.8cm or 10.5cm naval gun, and/or the 2cm flak gun. As the war progressed and Allied anti-submarine measures became far more effective, U-boats tended to remain submerged wherever possible, surfacing only when safe to do so in order to run the main diesel engines to recharge their batteries. Effectively, the deck gun was becoming redundant. Being little used, around April 1943 it was removed from the Type VII in order to save some weight and achieve a modest reduction in drag. At the same time, the danger from air attack having increased so much, U-boat flak defences were significantly enhanced. Despite the fact that several incidents are known where U-boats successfully fought off Allied air attacks, few U-boat commanders would willingly remain on the surface to engage an aircraft in combat unless diving was impossible or unsafe. The main deck armament therefore was only effectively used in the early part of the war, usually against lone ships or convoy stragglers in waters where there was relatively little chance of encountering enemy warships. The deck gun would have been used most often to ‘finish off a merchantman that had been damaged by torpedo, but had failed to sink. Expenditure of additional torpedoes would be considered wasteful when much cheaper and plentiful artillery shells could be used. The 8.8cm Deck Gun The 8.8cm gun used on U-boats was not directly related to the famous 8.8 or Acht-Acht flak gun which ultimately gained fame as an anti-tank weapon. More correctly entitled the 8.8cm Schiffskanone C/35; it was a purely naval weapon, developed from earlier weapons of this type used by the Imperial German Navy in World War I. The gun was mounted on a low pedestal forward of the conning tower and was traversable through 360 degrees. It could be depressed to -4 degrees and elevated up to 30 degrees. The gun fired a 13.7kg high explosive shell with a muzzle velocity of 700m/sec for a distance of up to 12,350m. It could also fire a 13.9kg armour-piercing shell or an 11.2kg star shell. When submerged, the barrel bore was protected by a waterproof tompion inserted into the muzzle. It was crewed by three men, the Kanonier (gunner), Ladeschütze (loader) and Richtschütze (gun-layer) supported by numerous other crewmen who would bring the ammunition up on deck from its storage under the floor plates of the Zentrale. On the deck, just forward and to port of the gun, was a small watertight ammunition locker giving the gun crew sufficient shells to allow the gun to be brought into action immediately whilst the bulk of the ammunition was retrieved from inside the boat. Two folding, padded, U-shaped supports were provided on both left and right sides of the gun for the gunner and gunlayer to steady themselves against rolling or pitching of the boat. In effect, the gun would be difficult to aim successfully in anything other than calm seas. In rough seas, the crew could strap themselves into position. Quite apart from being a poor gun platform, the narrow slippery deck of a U-boat was not a safe place to be in rough seas and gun crews would always be in danger of being washed overboard. The gun was controlled and directed, usually by the Second Officer (II Wach Offizier or IIWO), from the conning tower. The 10.5cm Deck Gun The standard deck gun fitted to the Type IX in the early part of the war was the 10.5cm Schiffskanone C/32 mounted in the identical pedestal fitting as used for the smaller 8.8cm weapon on the Type VII. Able to traverse through 360 degrees, it fired a 23kg projectile up to 15,300m. Alternatively, it could fire a 23.3kg armour-piercing shell or 14.7kg star shell. A crew of three was required to operate the gun, with additional crew members being engaged in keeping the gun supplied with ammunition from the magazine in the boat's interior. As the war progressed, it became clear that any benefits derived from the presence of the deck gun were offset by the increase in the drag imposed on the boat when moving under water. By 1943, most deck guns had been removed from Type VII’s, but for some reason most Type IX boats retained their 10.5cm guns. The principal exception to this was the Type IXD2, particularly those boats of this type operating in the Atlantic. One crewman operating a 2cm Zwillinge. This shot shows clearly how the gunner braced himself against two large curved, padded shoulder mounts. This weapon had a considerable recoil. The ‘spiderweb’ sight for the gun can also be seen here. The 2cm Flak Gun Two basic designs of 2cm flak gun (Flugabwehrkanone) were used. The earlier version, the 2cm Flak 30, was a single-barrelled weapon, with 360 degree traverse and capable of 2 degree depression and 90 degree elevation. It fired a 0.32kg shell with a range up to 12,350m. Maximum cyclic rate of fire was 480 rounds per minute, but effective use was around half this rate. A second, improved model, the 2cm Flak 38, was a very similar model but had an increased rate of fire at 960 rounds per minute. The second version was also produced in twin-barrelled (Zwilling) and four-barrelled (Vierling) versions. It was a direct development of a weapon designed for the army, and simply fitted to a naval pedestal mount (the Lafette C/35). The 3.7cm Flak Gun In the second half of the war, many U-boats received the 3.7cm Flak M742. Also an army weapon adapted for naval use, it fired a 0.73kg round up to 15,350m at a maximum rate of fire of 50 rounds per minute. Other Weapons As well as the main deck armament and flak defence weapons, a limited amount of small arms were kept on board the U-boat for use by boarding parties, guards when the boat was in dock, etc. These would include the 9mm or smaller 7.62mm pistol, 9mm sub-machine gun, 9mm machine gun and 7.92mm rifle. A small number of 7.92mm machine guns could also be carried to supplement the boat’s anti-aircraft armament. These could be fitted to mounts along the edge of the conning tower. A side view of the aft deck gun shows the relatively large size of the 3.7cm weapon, not significantly smaller than the 8.8cm forward deck gun on the Type VII. This gun was not specifically intended as a flak weapon, but was also for use against surface targets.