The union began in 1958 and existed until 1961, when Syria seceded from the union after the 1961 Syrian coup d'état. Egypt continued to be known officially as the "United Arab Republic" until 1971. The president was Gamal Abdel Nasser. The UAR was a member of the United Arab States, a loose confederation with the Mutawakkilite Kingdom of Yemen, which was dissolved in 1961.
Established on 1 February 1958, as a first step towards a larger pan-Arab state, the UAR was created when a group of political and military leaders in Syria proposed a merger of the two states to Egyptian President Gamal Abdel Nasser.
Pan-Arab sentiment traditionally was very strong in Syria, and Nasser was a popular hero-figure throughout the Arab world following the Suez War of 1956. There was thus considerable popular support in Syria for union with Nasser's Egypt. The Arab Socialist Ba'ath Party was the leading advocate of such a union.
In mid-1957 western powers began to worry that Syria was close to a Communist takeover; it had a highly organized Communist Party and the newly appointed army's chief of staff, Afif al-Bizri, was a Communist sympathizer. This caused the Syrian Crisis of 1957 after which Syrians intensified their efforts to unite with Egypt. Nasser told a Syrian delegation, including President Shukri al-Quwatli and Prime Minister Khaled al-Azem, that they needed to rid their government of Communists, but the delegation countered and warned him that only total union with Egypt would end the "Communist threat". According to Abdel Latif Boghdadi, Nasser initially resisted a total union with Syria, favoring instead a federal union. However, Nasser was "more afraid of a Communist takeover" and agreed on a total merger. The increasing strength of the Syrian Communist Party, under the leadership of Khalid Bakdash, worried the Syrian Ba'ath Party, which was suffering from an internal crisis from which prominent members were anxious to find an escape. Syria had had a democratic government since the overthrow of Adib al-Shishakli's military regime in 1954, and popular pressure for Arab unity was reflected in the composition of parliament.
When on 11 January 1958 al-Bizri led a Syrian delegation composed of military officers to Cairo, and personally encouraged Syrian-Egyptian unity, Nasser opted for a quick merger. Only Syrian advocates of unity, including Salah al-Din Bitar and Akram El-Hourani had prior knowledge of this delegation; Quwatli and Azem were notified a day later and considered it tantamount to a "military coup".
Nasser's final terms for the union were decisive and non-negotiable: "a plebiscite, the dissolution of parties, and the withdrawal of the army from politics". While the plebiscite seemed reasonable to most Syrian elites, the latter two conditions were extremely worrisome. They believed it would destroy political life in Syria. Despite these concerns, the Syrian officials knew it was too late to turn back.The members of the elite in Syria viewed the merger with Egypt as the lesser of two evils. They believed that Nasser's terms were unfair, but given the intense pressure that their government was undergoing, they believed that they had no other choice.
Egyptian and Syrian leaders signed the protocols, although Azem did so reluctantly. Nasser became the republic's president and very soon carried out a crackdown against the Syrian Communists and opponents of the union which included dismissing Bizri and Azem from their posts.