Tokens allow you to perform actions in Empire Wars.
When you first join a war, you get some number of tokens, between 10 and 30, depending on how long the war has been going on for. As time passes, you gain another token every few minutes, with the exact time depending on your Empire's Armory and whether or not you are asleep. The maximum number of tokens you can hold at any given time is 30 to 50(?) based on the Armory level.
The following Lieutenants can give you more tokens: