Complete the indicated task to unlock the achievement.

Achievement	How to unlock
Bronze General	Reach wave 5 on hard.
Bronze Rookie	Reach wave 5 on easy.
Bronze Veteran	Reach wave 5 on normal.
Gold General	Reach wave 15 on hard.
Gold Rookie	Reach wave 25 on easy.
Gold Veteran	Reach wave 25 on normal.
Master Emperor	Reach wave 5 on impossible.
Master Rookie	Reach wave 35 on easy.
Silver Rookie	Reach wave 15 on easy.
Silver Veteran	Reach wave 15 on normal.