to the training of Yemeni Army officers in Iraq. Later, several of them would play a key role in the 1962 coup d'état in North Yemen. The Kingdom of Yemen became a founding member of the Arab League in 1945 and joined the United Nations on 30 September 1947. It committed a small expeditionary force to the 1948 Arab–Israeli War. Instability and decline Imam Yahya was assassinated in an unsuccessful coup d'état in 1948, but his son, Imam Ahmad bin Yahya, regained power several months later. His reign was marked by growing development and openness, as well as renewed friction with the United Kingdom over the British presence in the south, which stood in the way of his aspirations to create a Greater Yemen. Imam Ahmad was slightly more forward-thinking than his father and was more open to foreign contacts. Nonetheless, his regime, like his father's, was autocratic and semi-medieval in character; even the most mundane measures required his personal approval. In March 1955, a coup by a group of officers and two of Ahmad's brothers briefly deposed the king but was quickly suppressed. Ahmad faced growing pressures, supported by the Arab nationalist and pan-Arabist objectives of the President of Egypt, Gamal Abdel Nasser, and, in April 1956, he signed a mutual defense pact with Egypt. In March 1958, Yemen joined the United Arab Republic (a federation of Egypt and Syria formed in February 1958) in a confederation known as the United Arab States. However, this confederation was dissolved in December 1961, soon after Syria withdrew from the United Arab Republic and the United Arab States in September 1961. Relations between Egypt and Yemen subsequently deteriorated. Imam Ahmad died in September 1962 and was succeeded by his son, Crown Prince Muhammad al-Badr, whose reign was brief. Egyptian-trained military officers inspired by Nasser and led by the commander of the royal guard, Abdullah as-Sallal, deposed him the same year he was crowned, took control of Sana'a, and created the Yemen Arab Republic (YAR). This sparked the North Yemen Civil War and created a new front in the Arab Cold War, in which Egypt assisted the YAR with troops and supplies to combat forces loyal to the imamate, while the monarchies of Saudi Arabia and Jordan supported Badr's royalist forces in opposing the newly formed republic. Conflict continued periodically until 1967 when Egyptian troops were withdrawn. By 1968, following a final royalist