The spoiling stance. An army that intends to win by breaking up what its opponent is trying to do rather than by out-scoring it directly.
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.
Disruption is the disposition on 5.2% of recorded tournament lists (61 lists).
Tyranids reaches for it most, on 17.6% of its lists, then Chaos Space Marines at 12.8%.