" Nasser’s new order appeared to be on the way when military officers, pledging “loyalty” to him, seized power in a coup in Syria. This led, in 1958, to a “merger” of Egypt and Syria into what was supposed to be a single country, the United Arab Republic. But then in 1961 other officers seized power in Damascus and promptly withdrew Syria from the new “state.” The following year, Nasser sent troops to intervene in the civil war in Yemen, expecting a quick victory that would expand his reach. Instead it turned into a long battle against royalist guerrillas and a proxy war between Egypt and Saudi Arabia. Iran joined with Saudi Arabia to support the guerrillas in resisting the Egyptian forces, one result of which was the establishment of an Iran-Arab Friendship Society, with offices both in Tehran and Riyadh. Nasser would end up calling Yemen his “Vietnam,” a political quagmire that added to the economic woes of the grossly mismanaged Egyptian economy. "

― Daniel Yergin , The New Map: Energy, Climate, and the Clash of Nations