Among the expressions we still use today …
Strafe: German for “punish.” The Germans used the phrase “Gott strafe England!” in propaganda. At the beginning of the war, the English began to use “strafe” in jokes to mean punish, bombard or reprimand. But by the end of the 4-year-conflcit, the word assumed the definition it retains: an attack of machine-gun fire from a low-flying aircraft.
Pipsqueak and whizz-bang: the sounds mortar shells make.
Camouflage: Technological advances such as the airplane and long-range artillery required the need to conceal troops.
Shell shock: What today we call PTSD was referred to as battle fatigue during World War II.
Cushy: Starting in the 19th century, Urdu words were picked up by the British military in India. With nearly 9 million forces mobilized from the British Empire to fight World War I, the word becomes popular and is used by civilians, too.