Allies:
British Commonwealth
Akko: Extended family
French Republic and Colonies
ClearlyInvsible: Great Grandfather (Régiment de Marche de Spahis Marocains)
Russian Empire
Walko: Unknown ancestor (Artillery)
Kingdom of Italy
United States of America
Akko: Various members (Army, Navy)
Locust: Great Granduncles (Army)
Other
Central:
German Empire
Empire of Austria-Hungary
Turin Turambar: Great Grandfather (Major, regiment unknown)
Ottoman Empire
Other
Unfortunately ladies and gentlemen, the War to end all Wars didn't live up to it's namesake. A lot of people fought and died in World War I, for both sides.
My Great-Grandfather was a cavalryman in that war. He rode horses in Europe and Greece, lost a foot and was gassed. He didn't win any medals, he was just another soldier. But he had a story none the less, and I'm sure your ancestors have one themselves.
We should remember those who fought in that conflict that started 100 years ago this year. So please, post who in your family fought along with their regiment and battles if you can. I'll make a list of everyone.