Anti-aircraft gun (M54)
Serious development of Allied air defence systems was motivated by the fact that enemy aircraft were the greatest threat early in the war.
The USA joined the war with structurally imperfect air defence guns, but after Great Britain requested that the USA provide it with manufacturing facilities to produce its own Bofors cannons, their drawbacks became all too apparent. This resulted in the creation of the M54, one of the most powerful air defence weapons of World War II. It was used by ground, naval, and air forces alike.
A great number of these guns was supplied to the USSR under Lend-Lease, and for a long time after that they could be found in different parts of the globe where Soviet influence was strong.