[1][2] A graduate of Harvard University, Barbour was one of the longest serving American diplomats in a foreign post, and was described by the Jerusalem Post as a "sagacious political intelligence who could continuously and precisely define for his own country and for his hosts the political aims of both, and more specifically the limits and tolerance of both."

[2] He remained at the post through the administration of Lyndon B. Johnson and passed up an appointment as Ambassador to the Soviet Union by Richard Nixon.

"[3] After the USS Liberty incident during the 1967 Six-Day War, Barbour played a crucial part in determining that the Israeli government had lied regarding certain aspects of their explanation as to how the attack happened.

ships in the area before the attack, Secretary of State Dean Rusk telegrammed the U.S. embassy in Tel Aviv and demanded “urgent confirmation.” Barbour confirmed that Israel’s story was bogus: “No request for info on U.S. ships operating off Sinai was made until after Liberty incident.

[citation needed] He was also a diplomat in Greece, Bulgaria, Italy, Iraq and Egypt, and in the early 1950s he was counselor of the U.S. Embassy in Moscow.