The phrase “The First World War” was used as early as 1918, by a journalist who felt it would not be the last.
A goat called Sergeant Bill became a Canadian war hero during WWI when he head-butted three soldiers into a trench to avoid an exploding shell.
The most decorated American WWI veteran from Texas was an undocumented Mexican immigrant named Marcelino Serna. He was also the first Hispanic to be awarded the Distinguished Service Cross.
During WWI, King Albert I of Belgium personally lead the desperate defense against the Germans, while the Queen served as a nurse, and their son, the 14 year-old Crown Prince enlisted in the infantry as a private.
In 1917, the U.S. War Industries Board asked women to stop buying corsets to free up metal for war production. This was said to have saved some 28,000 tons of metal, enough to build two battleships.
The British Army considered (and attempted) training seagulls to poo on enemy submarines periscopes before realizing that seagulls don’t fly that far out to sea.
In the US being clean shaven became popular after troops returned as heroes from WWI–they had been required to shave so gas masks would securely fit.
Amidst the chaos of WW1, a German unit tried to leave their trenches under a flag of truce on Easter Sunday, 1915. However, they were warned off by the British troops that opposed them.