He was the senior American diplomat chargé d'affaires in South Korea at the time of the 1961 coup d'état that brought Major-General Park Chung Hee to power.

Only weeks later, Green witnessed first hand the Transition to the New Order, an anti-communist purge in which Suharto led a coup against Sukarno following the murder of six generals by the 30 September Movement, which was blamed on the PKI by the Indonesian military based on dubious evidence.

[4] Green supported the Indonesian Army's version of the events,[5] but contemporary historians have challenged it, with historian Geoffrey B. Robinson of UCLA in particular noting that Green and other US officials involved in supporting the Suharto coup "published memoirs and articles that sought to divert attention from any possible US role, while questioning the integrity and political loyalties of scholars who disagreed with them.

[7][8] Recent revelations from government archives confirm that Green himself endorsed the Indonesian military "destroying PKI" through executions, noting in an October 20, 1965, telegram that he had "increasing respect for its determination and organization in carrying out this crucial assignment.

[citation needed] In 1973, President Nixon selected Green as United States Ambassador to Australia, a post he held until 1975.

[citation needed] Green retired from government service in 1979, joining the board of Population Crisis Committee, a non-profit committed to combating overpopulation.