War is always supposed to be a very serious business yet the wits will always find a way of cracking a joke or some other witticism to lighten the mood. Surprisingly even the German forces during WW2 had their fair share of jesters.
Main picture: Guard dog guarding the FLAK gun

A signalman and an officer [are Officers allowed to dig] of the Royal Canadian Corps of Signals digging a slit trench in France, July 1944

Blind date?

Col Anthony Joseph Drexel Biddle, hand-to-hand combat expert in 1943. He was known for ordering trainee marines to attempt to kill him with bayonets and disarming them all

Everybody needs a good counterweight but watch out for the hot brass

Hold your fire

German soldiers having fun during WW2

Royal Engineers being trained to probe for land mines in the dark in Italy during 1944

British espirit de corps during the summer of 1940

Two Calgary Highlanders stand by the banks of the Bow River, Calgary before departing for the war. They are humourously depicting Canada’s equipment shortages

Typical Aussie humour is reflected in this sign erected on the El Alamein Road by Australian troops on 14th September 1942

Donation of fresh beer

“Fritz, Don’t you hate it when it rains?” Bundesarchiv cc by sa 3.0