Skirmishers are light infantry or light cavalry soldiers deployed as a vanguard, flank guard or rearguard to screen a tactical position or a larger body of friendly troops from enemy advances. They are usually deployed in a skirmish line, an irregular open formation that is much more spread out in depth and in breadth than a traditional line formation. Their purpose is to harass the enemy by engaging them in only light or sporadic combat to delay their movement, disrupt their attack, or weaken their morale. Such tactics are collectively called skirmishing.