 Complete the following phrase:  In 1909, Shirases long-standing ambitions to lead a North Pole expedition were halted when two Americans, Frederick Cook and Robert Peary, each claimed independently to have reached the Pole. Although Cooks claim was quickly discounted, Pearys was widely accepted at the time. Having thus been forestalled, Shirase switched his attention instead to the South Pole. He would have to move quickly, as other expeditions, notably those of 