Ash Carter, the former Defense secretary who oversaw sweeping personnel changes at the Pentagon, including opening all military occupations and positions to women, has died at the age of 68, his family announced Tuesday. 

Carter, who ran the Defense Department from early 2015 to 2017 during President Obama’s second term, died Monday evening in Boston after a sudden heart attack, according to the family’s statement. 

While at the Pentagon, the 25th Defense secretary oversaw a range of national security issues, including the launch of the military strategy that would ultimately push back and defeat the Islamic State military group in Syria and Iraq. 

He also tackled numerous personnel matters, including ending a ban on transgender officers in the military and opening all military occupations and positions to women in 2016 — the first time in U.S. history that women could enter infantry, armor, reconnaissance and some special operations units previously only open to men.