Oerlikon. The oerlikon was a swedish manufactured 20mm cannon widely used by the allies.
Okinawa. the site of some of the bloodiest fighting in the pacific campaign.
Overlord. The operational codename for the D-day invasion of Normandy.
Oppenheimer, Robert J. father of the Atom Bomb.
Oscar. Allied codename for the Japanese fighter: Nakajima Ki-43 Hayabusa.
Ohka. Japanese rocket-powered suicide attack plane.
Omaha, one of the beaches at Normandy.
Oahu, the home island of Pearl Harbor.
Oberst, a German rank.
O2 the pay grade of an Army Lieutenat, O3, O4, etc..
Oklahoma as one of the Battleships.
Oleo as a replacement for butter.
O-Ring as a gasket.
Oblique as formation, (left or right).
Orders.
Officers.
Obligation (as in duty, honor and..)
Outhouse.
mustard gas
Some are
I'm not sure
Q Ships - which were merchant ships armed with camouflaged weapons which could be used against surface submarines.
One challenge faced by General George Washington at the start of the war was a lack of weapons.
Weight, ease of maintenance. SOME have a higher rate of fire.
The cold war started in 1945 after the World War II. The cold war was between Russia and some of the western countries. The existence of the nuclear weapons is what led to the development of the Cold war.
Two nuclear weapons ended World War 2.
Germany had thirty to forty different weapons in World War I. Some of these were artillery, pistols, special weapons such as a flame thrower, machine guns and ships.
Mustard gas, smoke bombs.
All countries fighting in World War 2 used weapons.
The physical weapons would have been mainly standard issue, add some clubs and ad hoc weapons.