Complex sentence: Once the squad has closed with the enemy it uses grenades and squad automatic fire to engage the enemy this allows a sufficient disruption of the enemy control of their defensive front to allow other squads to advance unopposed.
Split into simpler sentences: Once the squad has closed with the enemy it uses grenades and squad automatic fire to engage the enemy. This allows sufficient disruption of the enemy's control of their defensive front to allow other squads to advance unopposed.