Hold L2 R2 then press Right2, Down, Up. Left2.
After unlocking the Frag Grenade weapon challenge, complete all rounds and kill every enemy until round ten. If every enemy is killed, you will go into round eleven. In this round, the soldiers move and create the shape of first an "E", then an "A" as a reference to EA Games.
How to stay alive longer:
Alot of times you are alone doing a mission and you die fast when you can't see anyone. What you should do is try to form a group or fing a group of your own soldiers to join and you should stay in the middle. First and last always die first. always look different ways than your other members are so you have more coverage. ALWAYS ALWAYS ALWAYS enter a building with your group. They will have your back and try not to shoot them or else someone else can kill you. on the other team of course.