This is what we found on Wikipedia regarding the Ambush:

An ambush is a surprise attack carried out by people lying in wait in a concealed position. The concealed position itself or the concealed person(s) may also be called an "ambush". Ambushes as a basic fighting tactic of soldiers or of criminals have been used consistently throughout history, from ancient to modern warfare. The term "ambush" is also used in animal behavior studies, journalism, and marketing to describe methods of approach and strategy.

In the 20th century, a military ambush might involve thousands of soldiers on a large scale, such as at a choke point like a mountain pass. Conversely, it could involve a small irregular band or insurgent group attacking a regular armed-force patrol. Theoretically, a single well-armed, and concealed soldier could ambush other troops in a surprise attack.

In recent centuries, a military ambush can involve the exclusive or combined use of improvised explosive devices (IED). This allows attackers to hit enemy convoys or patrols while minimizing the risk of being exposed to return fire.