Deck guns

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 to sink merchant shipping, shell shore targets or defend the submarine on the surface. Typically a crew of three 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.

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.

The deck gun was introduced in all submarine forces prior to World War I. The three British M-class submarines mounted a single 12 inch (305 mm)/40 caliber naval gun intended to be fired while the submarine was at periscope depth with the muzzle of the gun above water, principally in a shore bombardment role. This World War I design was found unworkable in trials because the submarine was required to surface to reload the gun, and problems arose when variable amounts of water entered the barrel prior to firing.

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