He lifted a ban on transgender people serving in the military and opened up all roles to women.
Ash Carter's legacy may lie in his efforts to ensure a "lasting defeat" for the Islamic State groupFormer US Defence Secretary Ash Carter, who served in the final two years of Barack Obama's presidency, has died aged 68.As the country's 25th defence secretary, he oversaw the military strategy that pushed back the Islamic State group in Syria and Iraq.The policy change in 2016 allowed troops to transition gender while serving.
Mr Carter made other significant changes to the Department of Defense , such as opening all military occupations to women without exception for the first time. About 10% of positions were still closed to women at the time of the announcement in 2016. But Mr Carter's legacy may lie in his efforts to ensure a "lasting defeat" for Islamic State, something he later called "one of the defining issues of my time as secretary".
"Under his leadership, America accelerated its counterterrorism efforts, opened combat roles to women, modernised its weapons systems, and strengthened our alliances around the world, " said Mr Obama, adding his condolences to the Carter family.