Woodrow Wilson.
The Kaiser was the leader of Germany during WW1 (it means leader the same as Caesar and Czar), but he wasn't much of a participant.
There was no single leader during WW1. Each country had their own leader.
george bush
David Lloyd George was the leader of Brittain during ww1
Kaiser Wilhelm II
Franz Joseph
Kaiser Wilhelm II
John J. Pershing
King George V
It's influenza and the pandemic started the year WW1 ended
King George the 5th.