Professor Xavier and the X-Men #16

Xavier has a televised debate with mutant hating anthropologist, Bolivar Trask. During the broadcast, Trask unveils his Sentinels, robots who were built to capture and nullify mutants, but things quickly get out of hand as the Sentinels proclaim themselves superior to puny humans and prepare to take over. Xavier calls his X-Men to help and they return to battle the Sentinels. When one of their number falls, the giant robots capture Trask and return to their base. The X-Men follow and find a hidden complex complete with devastating weaponry aimed directly at them.