Archie to SAM: A Short Operational History of Ground-Based Air ...

ANTIAIRCRAFT DEFENSE THROUGH WORLD WAR II
billion on this problem, almost one-half of this amount on ammunition.
The Navy estimated that its antiaircraft guns increased
their effectiveness 100 times from the start to the finish
of the war. Mid- and short-range light antiaircraft guns presented
the major problem as the pre–World War II armament
(.50-caliber machine guns and 1.1-inch guns) proved inadequate.
The US Navy turned to foreign guns, the 20 mm Swiss
Oerlikon and the 40 mm Swedish Bofors.
The Navy estimated that the 20 mm cannon was eight to 10
times as effective as a .50-caliber machine gun and in 1935
bought some of the Swiss Oerlikons, even though Army and
Navy aircraft used the French Hispano Suiza 20 mm guns. By
war’s end, the Navy had 12,561 of the 20 mm guns shipboard
and had spent $787 million for one billion rounds of 20 mm
ammunition. The investment paid off. Between Pearl Harbor and
September 1944, the 20 mm guns downed 32 percent of all
Japanese aircraft claimed by Navy guns and 25 percent after
that date. Although the 20 mm guns did have certain advantages
over heavier guns, the 40 mm began to replace them toward
the end of the war (fig. 31). 92
The Bofors 40 mm gun was the most widely used antiaircraft
piece of World War II. The Swedes began the gun’s development
in 1928 and fielded the first units in the early 1930s.
It could fire a two-pound shell to an effective range of 1,500
yards at a rate of 120 shots per minute. The world took notice
when the British ordered the weapon in 1937, and, by 1939
the Swedes delivered the Bofors to 18 countries and concluded
production licenses with 11 others. Both sides manufactured
and used Bofors during the war.
The Navy’s interest in the Bofors 40 mm gun began in the
fall of 1939; and, in late August 1940, guns and equipment arrived
in the United States (fig. 32). Tested in September, the
Bofors guns proved superior to both the US 37 mm and the
British two pound (pom pom). The US government signed a
contract in June 1941 and installed the first 40 mm Bofors
aboard ship early the next year. But, there were problems in
manufacturing the Bofors. First, the original metric drawings
had to be converted to English measurements; second, it was
found that the two American manufacturers used different sys-
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