Indirect fire is a military (specifically ground forces) term which indicates a means of bombarding the enemy which operates using arc trajectories and thus does not require a direct line-of-sight between the firing unit (typically less well-armored than a frontline unit) and the target. Rockets, howitzers, mortars; anything which travels in an arc (and could thus be sited, say, behind a hill) counts. Indirect fire leads to higher reconnaissance requirements, as the shooters can no longer see their targets and rely on relayed information to correct their aim and for battle damage assessment. It is typically used in fire support missions.