Overwatch is an important ground tactic that we employ when advancing on buildings or an objective area.
Wikipedia wrote …
In modern warfare, overwatch is the state of one small unit or military vehicle supporting another unit, while they are executing fire and movement tactics. An overwatching, or supporting unit has taken a position where it can observe the terrain ahead, especially likely enemy positions. This allows it to provide effective covering fire for advancing friendly units. The term overwatch originates in U.S. military doctrine.
An ideal overwatch position provides cover for the unit, and unobstructed lines of fire. It may be on a height of ground or at the top of a ridge, where a vehicle may be able to adopt a hull-down position. If the overwatching unit is in a position to fire over advancing friendly units, great care must be taken not to let fire fall short. The friendly units should be within tracer burnout (the range at which tracer rounds are visible).
Overwatch can be performed by platoons during company fire and movement, by individual armoured fighting vehicles (especially tanks) or infantry sections, in platoon fire and movement, or even by fireteams or individual soldiers, in the final stages of an assault.
Overwatch tactics and firing at the short halt were especially important in armoured warfare before modern tank gun stabilizers were developed, since moving tanks were unlikely to hit any target. Even in modern tanks, however, it is much easier to spot enemies at a halt.
Having an overwatch position during any ground engagement is highly advantageous to the mission outcome. Typically we emplace snipers and/or heavy assaults with supporting engineers to provide both ammo and rear security. In any case, overwatch should also take advantage of their position to provide accurate intelligence data on the position and movement of enemy forces, as they tend to have the best vantage point of an objective.
In the case of heavy assaults on overwatch, the heavy assaults put down seemingly excessive amounts of fire and “Walk” friendly assault elements across the objective by putting fire down on any positions that the enemy might be able to use to engage the assault element. The idea here is to achieve and maintain fire superiority.
In the case of an assault on a building, the overwatch position would put fire into windows and doors on the side of the building that the assault element intends to breach. In this case the overwatch is typically shooting over the heads of the assault element making it extremely important for whoever is in charge of the overwatch position to pay close attention to the position of the assault element. The overwatch should also be visually scanning left and right of the building to look for threats outside of the building that may cause problems for the assault element.
In any case of overwatch providing supporting fires, fratricide is a very high possibility and every member of overwatch should be looking for friendlies and where their rounds are landing. A shot taken at an enemy that is at risk of hitting a friendly is a bad shot that should NOT be taken.