The hammer and anvil is a classic military tactic which has been used since the beginning of organized warfare. From the ancient world, in which it was used by Alexander the Great and the Roman Generals, to the Vietnam War it has been used by Generals from every empire and nations.
In ancient times the hammer and anvil tactic consisted of a diversionary frontal assault carried out by an infantry formation against the enemy front line, while the cavalry swung aroung to the enemy rear to attack it from behind. The hammer and anvil tactic began with two enemy infantry units of varying strengths clashing in a frontal assault. While the rival infantry units fought one another, fixed in the engagement, a cavalry force maneuvered around the enemy and attacked from behind, hammering and pushing it hard against the friendly infantry line, which functioned as an anvil. In order to be successful, the force attempting the maneuver had to possess a superior amount of cavalry.
In Vietnam, hammer and anvil was an infantry strategy of surrounding an enemy base area, then sending in other units, such as airmobile cavalry that used armed helicopters (UH-1) to drive the enemy out of hiding into a clearing where the communist force was mauled by the waiting friendly infantry units using machine guns and mortars. In this case, the helicopters hammered the enemy out against a strategically deployed friendly infantry force.