US president Barack Obama has nominated physicist Ashton Carter as secretary of defence – one of the key positions in the US cabinet. With a DPhil in theoretical physics from Oxford University, the 60 year old has extensive experience in government and academia, working predominantly on national security and military issues. His nomination will first require confirmation by the US Senate, but insiders indicate that Carter's passage will be smooth. "I can't imagine that he's going to have opposition to his confirmation," says Oklahoma senator James Inhofe, a Republican who is frequently at odds with the Obama administration.

Carter was not talking to the media – a tradition among government nominees until they have appeared before the Senate. However, former colleagues have praised Carter as being capable of performing the task of overseeing US defence policy. "He comes grounded in the conceptualization of a physicist – he is very good in policy areas," Graham Allison of Harvard University's Belfer Center for Science and International Affairs told Physics World. "Both his intellectual foundation and his work as a practitioner in government have been informed by evidence-based analysis, as opposed to hocus-pocus."

From physics to the Pentagon

Carter earned a degree in physics and medieval history from Yale University in 1976, and won a Rhodes Scholarship to Oxford, where he chose to concentrate on physics, graduating in 1979. "My arrogant view at the time was that life would eventually teach me political science, sociology, psychology and even economics, but it would never teach me linear algebra," he wrote in a short autobiography for the Belfer Center.

In 1981, following a year as a research associate in theoretical physics at Rockefeller University, and another in the Congressional Office of Technology Assessment, he joined the Pentagon as a civilian programme analyst. Three years later, he applied his background in physics to missile defence, dubbing former US president Ronald Reagan's "Star Wars" nuclear-weapons defence system as "unworkable".

Between 1984 and 1993, Carter then held a variety of academic positions at the Massachusetts Institute of Technology and Harvard, focusing on international affairs and becoming an expert on defence issues and international security. He rejoined the Pentagon in 1993 as assistant secretary of defence for international security policy. There, he helped to secure nuclear weapons in Eastern Europe following the collapse of the former Soviet Union.

After some years in industry and academia, during which he wrote three books and contributed a multitude of journal and popular-science articles, Carter returned to government in 2009 as undersecretary of defence for acquisition, technology and logistics. In that position, he earned praise for his ability to guide the defence department through the government sequester, which forced all departments to reduce their spending, with minimal damage to military readiness.

Carter became deputy to defence secretary Leon Panetta from 2011 to 2013. In that role, he identified and carried out cuts to the military budget mandated by Congress. Panetta compared him to Scotty, the engineer in Star Trek: "I worked on the bridge while he manned the engine room," Panetta wrote in his recent book Worthy Fights: A Memoir of Leadership in War and Peace.

Challenges ahead

Carter was tipped to replace Panetta when the latter left the defence department two years ago, but the Obama administration instead selected former Nebraska Senator Chuck Hagel. Hagel's retirement from the position, announced in November, has now opened the way for Carter, who is currently lecturing at Stanford University.

Once confirmed, Carter will face fresh challenges within a tightly controlled financial situation, including the struggle with Islamic State in the Middle East, the small but continuing US military presence in Afghanistan and Iraq, and maintaining a US military presence in Asia. "We are trying to manage on a lower budget at a time when the threat is not receding," Carter told the Boston Globe in 2012. "The world hasn't gotten any safer."