The scouting stance. An army that intends to win on speed and position: being where the opponent is not.
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.
Reconnaissance is the disposition on 10.9% of recorded tournament lists (40 lists).
Chaos Knights reaches for it most, on 85.7% of its lists, then Dark Angels at 26.1%.