Sneak attack

An ambush is a long-established military tactic in which combatants take advantage of concealment and the element of surprise to attack unsuspecting enemy combatants from concealed positions, such as among dense underbrush or behind hilltops. Ambushes have been used consistently throughout history, from ancient to modern warfare. In the 20th century, an ambush might involve thousands of soldiers on a large scale, such as over a choke point such as a mountain pass, or a small guerrilla band or insurgent group attacking a regular armed force patrol.

The use by early humans of the ambush may date as far back as two million years when anthropologists have recently suggested that ambush techniques were used to hunt large game.

One example from ancient times is the Battle of the Trebia river. Hannibal encamped within striking distance of the Romans with the Trebia River between them, and placed a strong force of cavalry and infantry in concealment, near the battle zone. He had noticed, says Polybius, a "place between the two camps, flat indeed and treeless, but well adapted for an ambuscade, as it was traversed by a water-course with steep banks, densely overgrown with brambles and other thorny plants, and here he proposed to lay a stratagem to surprise the enemy". When the Roman infantry became entangled in combat with his army, the hidden ambush force attacked the legionnaires in the rear. The result was slaughter and defeat for the Romans. Nevertheless, the battle also displays the effects of good tactical discipline on the part of the ambushed force. Although most of the legions were lost, about 10,000 Romans cut their way through to safety, maintaining unit cohesion. This ability to maintain discipline and break out or maneuver away from a kill zone is a hallmark of good troops and training in any ambush situation. (See Ranger reference below).

Another famous ambush was that sprung by Germanic warchief Arminius against the Romans at Battle of the Teutoburg Forest. This particular ambush was to affect the course of Western history. The Germanic forces demonstrated several principles needed for a successful ambush. They took cover in difficult forested terrain, allowing the warriors time and space to mass without detection. They had the element of surprise, and this was also aided by the defection of Arminius from Roman ranks prior to the battle. They sprang the attack when the Romans were most vulnerable; when they had left their fortified camp, and were on the march in a pounding rainstorm.

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Wikipedia