 Finally , in September , there was Operation Comet , in which the division 's three brigades were to land in the Netherlands and each capture a river crossing . The first of these was the bridge over the River Waal at Nijmegen , the second the bridge over the River Maas at Grave , and the last was the bridge over the River Rhine at Arnhem . Planning for Comet was well advanced when on 10 September the mission was cancelled . Instead , a new operation was proposed with the same objectives as Comet but to be carried out by three divisions of the First Allied Airborne Army . 
