ashton baldwin "ash" carter (september 24, 1954 – october 24, 2022) was an american politician, military civillian official and academic. he was the united states secretary of defense from 2015 to 2017. he is also a physicist and a former harvard university professor of science and international affairs. he was nominated by president barack obama, and confirmed by the senate by a vote of 93–5, to replace chuck hagel as the us secretary of defense.