The hammer and anvil is a military tactic involving the use of two primary forces, one to pin down an enemy, and the other to smash or defeat the opponent with an encirclement maneuver. It may involve a frontal assault by one part of the force, playing a slower-moving or more static role. The second phase involves a more mobile force that maneuvers around the enemy and attacks from behind or the flank to deliver a decisive blow. The "hammer and anvil" tactic is fundamentally a single envelopment, and is to be distinguished from a simple encirclement where one group simply keeps an enemy occupied, while a flanking force delivers the coup de grace. The strongest expression of the concept is where both echelons are sufficient in themselves to strike a decisive blow. The "anvil" echelon here is not a mere diversionary gambit, but a substantial body that hits the enemy hard to pin him down and grind away his strength. The "hammer" or maneuver element succeeds because the anvil force materially or substantially weakens the enemy, preventing him from adjusting to the threat in his flank or rear. Other variants of the concept allow for an enemy to be held fast by a substantial blocking or holding force, while a strong echelon, or hammer, delivers the decisive blow. In all scenarios, both the hammer and anvil elements are substantial entities that can cause significant material damage to opponents, as opposed to light diversionary, or small scale holding units.
Antiquity
Battle of Issus The tactic was used in Antiquity, as the maneuver's origins used light cavalry, ubiquitous in the ancient world. The tactic also worked with the heavy cataphracts of the Eastern world. It appeared in a number of battles fought by the ancient Greeks and Romans. In addition to being used in many of Alexander the Great's battles, it was also used during the Second Punic War during the Battle of Cannae and the Battle of Zama.
Battle of Pharsalus
In 48 BC, Pompey the Great attempted to use it against Julius Caesar at the Battle of Pharsalus, in what was to be the decisive battle of the Great Roman Civil War. Caesar countered this by ambushing Pompey's "hammer" element with a hidden fourth line of infantry; Pompey's infantry was to be the anvil while his cavalry 'hammer' encircled Caesar's right flank. There was significant distance between the two armies, according to Caesar. As the infantry of Caesar advanced, Pompey ordered his men not to charge, but to wait until Caesar's legions came into close quarters; Pompey's adviser Gaius Triarius believed that Caesar's infantry would be fatigued and fall into disorder if they were forced to cover twice the expected distance of a battle march. Also, stationary troops were expected to be able to defend better against pila throws. Seeing that Pompey's army was not advancing, Caesar's infantry under Mark Antony and Gnaeus Domitius Calvinus started the advance. As Caesar's men neared throwing distance, without orders, they stopped to rest and regroup before continuing the charge; Pompey's right and centre line held as the two armies collided. Caesar countered this by positioning the reserves of his 4th line to intercept the attacking cavalry. As Pompey's infantry fought, Labienus ordered the Pompeian cavalry on his left flank to attack Caesar's cavalry; as expected they successfully pushed back Caesar's cavalry. Caesar then revealed his hidden fourth line of infantry and surprised Pompey's cavalry charge; Caesar's men were ordered to leap up and use their pila to thrust at Pompey's cavalry instead of throwing them. Pompey's cavalry panicked and suffered hundreds of casualties, as Caesar's cavalry came about and charged after them. After failing to reform, the rest of the Pompey's cavalry retreated to the hills, leaving the left wing of Pompey's legions exposed to the hidden troops as Caesar's cavalry wheeled around their flank. Caesar then ordered in his third line, containing his most battle-hardened veterans, to attack. This broke Pompey's left wing troops, who fled the battlefield. After routing Pompey's cavalry, Caesar threw in his last line of reserves. Pompey lost the will to fight as he watched both cavalry and legions under his command break formation and flee from battle, and he retreated to his camp, leaving the rest of his troops at the centre and right flank to their own devices. He ordered the garrisoned auxiliaries to defend the camp as he escaped. As the rest of Pompey's army were left confused, Caesar urged his men to end the day by routing the rest of Pompey's troops and capturing the Pompeian camp. They complied with his wishes; after finishing off the remains of Pompey's men, they furiously attacked the camp walls. The Thracians and the other auxiliaries who were left in the Pompeian camp, in total seven cohorts, defended bravely, but were not able to fend off the assault.
Early modern era to World War I
The Ashanti versus the British – 1874
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