Naval forces in the 1930s

In the age before intercontinental air travel, control of the sea was the primary assurance of national defense. Nations relied upon their navies to protect their soil; however, navies were expensive organizations, and the major powers tried to limit naval armaments to reduce costs and lower the threat of naval competition that might trigger another world war.

Naval forces during the 1930’s faced a number of challenges stemming from international treaties intended to limit naval armament and prevent future wars. In 1922, the United States, Great Britain, Japan, France, and Italy agreed to the Washington Naval Treaty, which limited the size and number of battleships and aircraft carriers each country could possess. In 1930, the nations agreed to the London Naval Treaty, which limited the number of cruisers, destroyers, and submarines that each fleet could possess. Together, the two treaties imposed strict limits on size, firepower, and capability of each ship type, forcing navies to innovate and compromise on ship design.

Battleships, long the centerpiece of naval power, were a particular problem. The Washington Treaty imposed a ten-year “battleship holiday,” meaning treaty signers agreed not to construct any battleships for ten years; this agreement was renewed in 1930. As battleships aged, navies had to reconstruct and rebuild their battleships to ensure their effectiveness. Older battleships received a variety of improvements throughout the 1930’s. Coal-fueled ships were converted to oil-fueled ships, side “bulges” was added to absorb torpedo hits, and deck armor to counter air-dropped bombs was added. Battleships also received new equipment during the 1930’s, such as improved fire-control systems and antiaircraft guns to deal with the aerial threat.

Aircraft carriers, also limited by the Washington Treaty, became a more prominent part of the world navies, first as reconnaissance platforms and then as attack weapons. The first aircraft carriers in the U.S. Navy were converted battle-cruiser hulls, but the first purpose-built aircraft carriers appeared during the 1930’s, starting with USS Ranger in 1934. Allowed only a limited tonnage of aircraft carriers, the U.S. Navy debated whether more small carriers or fewer larger carriers were preferable. Ranger, at fifteen thousand tons, represented the small-carrier theory. The ship was too cramped for effective service, however, and the next class of aircraft carriers, the Yorktown class, began service in 1937 at a displacement of twenty thousand tons.

The same debate on tonnage distribution also affected submarine construction after the United States signed the London Treaty. As it had with aircraft carriers, the U.S. Navy opted to build a smaller number of large submarines with operations in the Pacific Ocean in mind. The U.S. Navy viewed Japan as its most likely adversary in a future war, so it needed large submarines with long range to patrol the vast expanse of the Pacific. The Salmon class submarines of 1937, for example, displaced nearly three thousand tons and had a range of more than eleven thousand miles.

Size was also an issue for American destroyers. Some strategists in the U.S. Navy wanted small destroyers as battle-fleet escorts, requiring only guns and depth charges to ward off enemy destroyers and submarines. However, other officers wanted large destroyers with a heavy torpedo armament so destroyers could act as fast-attack forces on their own. Eventually, the heavy destroyer won out, as demonstrated by the 1936 Benham-class destroyers armed with four 5-inch guns and eight 21-inch torpedo tubes on a displacement of twenty-four hundred tons.

The allocation of cruiser tonnage, however, was the most contentious debate, because cruisers could do so many things. Various strategists wanted cruisers to escort the battle fleet, while others viewed them as advanced battle-fleet scouts; others still perceived cruisers as a separate offensive wing of the fleet. Again, the debate between “heavy” cruisers armed with relatively few 8-inch guns versus “light” cruisers armed with more 6-inch guns emerged. In the immediate aftermath of the London Treaty, the U.S. Navy opted for heavy cruisers, such as the 1933 Portland class, with nine 8-inch guns. In 1935, however, the Japanese navy commissioned the first Mogami class light cruiser with a massive armament of fifteen 6-inch guns. In reply, the U.S. Navy began construction of similar vessels: the Brooklyn class, which entered service in 1937, with an armament similar to the Mogami class ships. The U.S. Navy concentrated on light-cruiser construction thereafter.

During the late 1930’s, weight requirements ceased to matter. Unhappy with the treaty tonnage allocations that placed its navy behind those of the United States and Great Britain, in 1936 Japan announced that it was no longer abiding by the agreements. That, in turn, freed the other treaty signers to increase the size of their ships and fleets. The United States responded by authorizing the North Carolina- and South Dakota-class battleships—thirty-six thousand tons and thirty-five thousand tons, respectively—and the heavy Essex- and light Independence-class aircraft carriers—thirty-six thousand tons and eleven thousand tons, respectively. Other ship types during the late 1930’s also grew in displacement, such as the Cleveland-class light cruisers, at fourteen thousand tons; the Fletcher-class destroyers, at twenty-five hundred tons; and the Tambor-class submarines, at twenty-four hundred tons.

In addition to warship construction, naval forces during the 1930’s introduced other technological and tactical innovations. Aircraft carriers came into their own during the 1930’s. At first, navies centered on battleships considered the aircraft to be simply a launch platform for scout planes to locate the enemy for the battleships to engage. Improvements in aircraft, however, meant that aircraft carriers became offensive weapons in their own right. Besides fighter aircraft to defend the fleet, aircraft carriers could attack enemy ships with their torpedo bombers or dive bombers. First developed during the 1920’s, torpedo bombers flew in at low levels to launch their torpedoes at an enemy ship. A tactic introduced in the 1930’s, however, was dive-bombing, where an aircraft swooped down from high altitude to low altitude in a steep dive, literally flying the bomb directly into the target before pulling out of the dive and flying away. The U.S. Navy in particular favored dive bombing as more accurate than torpedo attacks, acquiring its first specialized dive bomber, the Curtiss F8C Helldiver, in 1929.

Although often perceived as an element of World War II, the first electronic equipment began to appear on naval ships during the 1930’s. In 1935, the U.S. Navy introduced the MK 37 Gun Fire Control System, a complex electromechanical aiming system for medium-caliber guns on destroyers and cruisers. The MK 37 provided central aiming data for antiaircraft guns shooting at fast-moving enemy aircraft, data that the gun crews themselves could not calculate. Submarines also received an electromechanical aiming device for its torpedoes, the Torpedo Data Computer, developed during the late 1930’s and first deployed in 1940. The Torpedo Data Computer calculated a variety of variables, such as the speed of the submarine and the speed and distance of the target, to calculate firing solutions against enemy targets at high angles of deflection. For navigation, ships received radio direction finders to reference their position relative to fixed radio emitters on shore. In 1931, the U.S. Navy introduced its first submarine-detecting sonar system, code-named the “QB,” which emitted a supersonic sound wave into the water from a hydrophone array under the bow of the ship.

Impact

The treaties that limited naval armament during the early 1930’s ultimately failed, and the ships designed and introduced during the late 1930’s became the cornerstone of the massive fleets that battled in World War II. The weaponry and ships of the era shaped how the fleets of the world fought the battles of the 1940’s. Battleships still played a role but were surpassed by the aircraft carrier as the primary fleet weapon, as their torpedo planes and dive bombers could dominate a naval battle at ranges far beyond those of a battleship’s guns. The early electronic devices of the 1930’s also expanded into full-blown electronic warfare during the 1940’s.

Bibliography

Felker, Craig C. Testing American Sea Power: U.S. Navy Strategic Exercises, 1923-1940. College Station: Texas A&M University Press, 2007. Faced with the limits of existing naval treaties, the U.S. Navy used naval exercises to test its capabilities with its limited number of ships.

Goldman, Emily O. Sunken Treaties: Naval Arms Control Between the Wars. University Park: Pennsylvania State University Press, 1994. Discussion of the failure of the Washington, D.C., and London treaties by placing the agreements in the context of diplomatic and nationalistic goals.

Kuehn, John T. Agents of Innovation: The General Board and the Design of the Fleet That Defeated the Japanese Navy. Annapolis, Md.: Naval Institute Press, 2008. Institutional study of the General Board of the United States Navy, an organization that shaped requirements, designs, and construction of ships in the interwar period.

Marriott, Leo. Treaty Cruisers: The First International Warship Building Competition. London: Pen and Sword, 2005. A discussion of how the major navies accommodated, and sometimes cheated on, the London Treaty in their 1930’s cruiser construction programs.

Murray, Williamson R. Military Innovation in the Interwar Period. New York: Cambridge University Press, 1998. Although the book also depicts land and air innovations, most of the pages are devoted to the creative means by which navies accommodated the restrictive treaties.