Complex sentence: During 1999 two British soldiers were killed and 17 injured whilst resupplying the patrol bases; and, subsequently, the land convoys were stopped and replaced by aerial resupply with helicopters and Hercules transport aircraft.
Split into simpler sentences: During 1999 two British soldiers were killed and 17 injured whilst resupplying the patrol bases. The land convoys were subsequently stopped and replaced by aerial resupply with helicopters and Hercules transport aircraft.