Former US Defence Secretary Ash Carter, who served in the final two years of Barack Obama’s presidency, has died aged 68.
He suffered a sudden cardiac event in Boston on Monday, his family said.
As the country’s 25th defence secretary, he oversaw the military strategy that pushed back the Islamic State group (IS) in Syria and Iraq.
Mr Carter is also credited with lifting the ban on transgender people serving in the US military.
The policy change in 2016 allowed troops to transition gender while serving. It also set standards for medical care and prevented service members from being discharged or denied re-enlistment based on their gender identity.
The move, which was phased in during the final year of the Obama presidency, was rolled back one year later by former President Donald Trump. It has since been reinstated by President Joe Biden.
Mr Carter made other significant changes to the Department of Defense (DoD), 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.
In so doing, Mr Carter overrode a request by the Marine Corps to exempt women from certain roles, including in infantry and machine gunnery. “We are a joint force and I have decided to make a decision which applies to the entire force,” he said at the time.
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”.
Taking the reins at a time when the US and its coalition partners still lacked a comprehensive plan for success on the battlefield, he helped launch an “accelerated” campaign to liberate IS strongholds and force the group’s fighters from the pockets of territory they controlled.
IS no longer controls large swathes of Iraq and Syria as it did at the height of its power. The group lost its last territory in Syria in 2019, but small cells of its fighters continue to carry out attacks in both countries.
A statement from Mr Obama lauded Mr Carter as a leader who made the world “safer” during his lifetime.
“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.
According to the DoD’s website, Mr Carter was “in direct and indirect service of eleven secretaries of defence in both Democratic and Republican Administrations” over a career that spanned three decades.
After leaving government, he led the Belfer Center for Science and International Affairs at Harvard University’s Kennedy School.
“He devoted his professional life to the national security of the United States and teaching students about international affairs,” his family said in a statement. “His sudden loss will be felt by all who knew him.”