Roman War Tactics: The Wedge

The wedge was commonly used by attacking legionaries, – legionaries formed up in a triangle, the front 'tip' being one man and pointing toward the enemy, – this enabled small groups to be thrust well into the enemy and, when these formations expanded, the enemy troops were pushed into restricted positions, making hand-to-hand fighting difficult. This is where the short legionary gladius was useful, held low and used as a thrusting weapon, while the longer Celtic and Germanic swords became impossible to wield.
Via: getspacey.blogspot.com/