At the beginning of your upkeep, put a muster counter on Assemble the Legion. Then put a 1/1 red and white Soldier creature token with haste onto the battlefield for each muster counter on Assemble the Legion.
Official Rulings for Assemble the Legion
1/24/2013 : If Assemble the Legion isn't on the battlefield when its ability resolves, use the number of muster counters it had when it was last on the battlefield to determine how many Soldier tokens to put onto the battlefield.
Others who bought Assemble the Legion also bought...