Robert Green served for 20 years in the Royal Navy, from 1962–82. As a Fleet Air Arm Observer/bombardier-navigator, he flew in Buccaneer nuclear strike aircraft and anti-submarine helicopters. On promotion to Commander in 1978, he worked in the Ministry of Defence before his final appointment as Staff Officer (Intelligence) to the Commander-in-Chief Fleet. Having taken voluntary redundancy in 1981, he was released after the 1982 Falklands War and trained as a roof-thatcher in Dorset.

In 1984, the murder of his beloved aunt and mentor Hilda Murrell led him to examine and then challenge the hazards of nuclear electricity generation. This, plus the break-up of the Soviet Union followed by the 1991 Gulf War, caused him to speak out against nuclear weapons – one of the first ex-Commanders with nuclear weapon experience to do so.

Commander Green chaired the British affiliate of the World Court Project (1991–2004), an international citizen campaign that led to the International Court of Justice judgment in 1996 that the threat or use of nuclear weapons would generally be illegal. He is now Co-Director with his wife, Dr Kate Dewes ONZM, of the Disarmament & Security Centre in New Zealand. His previous book, Security Without Nuclear Deterrence, was published in 2010.