Deck gun

A deck gun is a type of naval artillery mounted on the deck of a submarine. Similar unenclosed guns are often found on surface ships as secondary or defensive armament, although the term "deck gun" normally refers only to submarine-mounted guns. Most submarine deck guns were open, however a few larger submarines placed these guns in a turret.

The deck gun was used as a defensive weapon against smaller boats or ships and in certain cases where torpedo use was limited. Typically a crew of three; gunner, loader and layer (pointer, trainer, and loader in the US), operated the gun, while others were tasked with supplying ammunition. A small locker box held a few 'ready-use' rounds. With a well-drilled, experienced crew, the rate of fire of a deck gun could be 15 to 18 aimed shots per minute.

The deck gun was introduced in all submarine forces prior to World War I. Although technically not a deck gun, USS Holland (SS-1), the first American submarine, was equipped with a pneumatic dynamite gun built into the bow in 1900. The deck gun was first used by the Germans in World War I, and proved its worth when the U-boat needed to conserve torpedoes or attack enemy vessels straggling behind a convoy. Submarine captains often considered the deck gun as their main weapon, using torpedoes only when necessary, since many World War I submarines carried 10 or fewer torpedoes and typically fired several simultaneously to increase the probability of hitting the target. Lothar von Arnauld de la Perière used a deck gun or a dynamiting team on 171 of his 194 sinkings.

In early World War II, German submarine commanders favored the deck gun because of the unreliability of torpedoes. The deck gun became less effective as convoys became larger and better equipped, and merchant ships were armed. Surfacing also became dangerous in the vicinity of a convoy because of improvements in radar and direction finding. (See Defensively equipped merchant ships (DEMS) and United States Navy Armed Guard). German U-boat deck guns were eventually removed on the order of the supreme commander of the U-boat Arm (BdU) during World War II, and those deck guns that remained were no longer manned.

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