The killing stance. An army that intends to win by taking the opposing army off the board.
Your Force Disposition comes out of the detachments you take when you build the army, so it is settled before the game begins, and it fixes which five primary missions you can ever be dealt.
Purge the Foe is the disposition on 23.4% of recorded tournament lists (416 lists).
Deathwatch reaches for it most, on 71.4% of its lists, then World Eaters at 65.6%.