With Giant II cancelled, Operation Giant I was reactivated to drop two battalions of the 504th PIR at Capua on September 13. However, significant German counterattacks, beginning on September 12, resulted in a shrinking of the American perimeter and threatened destruction of the Salerno beachhead. As a result, Giant I was cancelled and the 504th PIR instead dropped into the beachhead on the night of September 13 using transponding radar beacons as a guide. The next night the 505th PIR was also dropped into the beachhead as reinforcement. In all, 3,500 paratroopers made the most concentrated mass night drop in history, providing the model for the American airborne landings in Normandy in June 1944. An additional drop on the night of September 14–15 of the 509th PIB to destroy a key bridge at Avellino, to disrupt German motorized movements, was badly dispersed and failed to destroy the bridge before the Germans withdrew to the north.