A decades-long defense wonk who gradually ascended to the Pentagon's top job, Carter helped oversee the launch of a military strategy that would drive back the Islamic State militant group in Syria and Iraq, and ultimately defeat the organization."Carter always set politics aside; he served presidents of both parties over five administrations, holding multiple positions within the Department of Defense," his family said in the statement.Carter held a doctorate in theoretical physics from Oxford University, and on at least one occasion overseas even spoke to the media traveling with him about black holes.He tried, with limited success, to bridge a gaping divide between the Pentagon and Silicon Valley to bring technological innovations to the Defense Department more quickly.Since leaving public service, Carter led the Belfer Center for Science and International Affairs at Harvard's Kennedy School."