Cox was educated at the University of Reading. He has taught at Queen's University Belfast (1972–1995), San Diego State University (1986), the College of William and Mary in Virginia (1987–1989), the University of Wales, Aberystwyth (1995–2001), the Catholic University of Milan (2003 and 2004) and the University of Melbourne (2004). He was also a Visiting Professor at the Centre for Defence and Strategic Studies in Canberra, Australia, between 2003 and 2004. In 2003, he became a Chair at the London School of Economics.