skirmish

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 much more spread out in depth and breadth than a traditional line formation. Their purpose is to harass the enemy – engaging them in only light or sporadic combat in order to delay their movement, disrupt their attack, or weaken their morale; these tactics are collectively called skirmishing.
A battle with only light, relatively indecisive combat is often called a skirmish, even if heavier troops were sometimes involved.
Skirmishers can be either regular army units temporarily detached to perform skirmishing, or specialty units specifically armed and trained for such low-level irregular warfare tactics. Light infantry, light cavalry, and irregular units often specialize in skirmishing. Skirmishers' open formations and smaller numbers can give them superior mobility over the regular forces, allowing them to only engage on favorable terms, taking advantage of better position or terrain and quickly withdrawing from any threat of superior enemy forces.
Though often critical in protecting the main army from sudden enemy advances, skirmishers are poor at taking or defending ground from heavy infantry or heavy cavalry. In modern times, following the obsolescence of such heavy troops, all infantry has become indistinguishable from skirmishers, and the term has effectively lost its original military meaning as a distinct class of soldier, although skirmishing as a combat role is commonplace.

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