Imam Ahmad reversed the isolationist policies of his father and opened Yemen's economy and society to the outside world. It went as the theocratic and largely medieval Imamate which became the first Arab state to accept Soviet aid. Beginning in 1955 Yemen entered into various treaties of friendship and from 1957 began receiving large amounts of Soviet arms as well as Soviet and Chinese military advisers. When the imam went abroad owing to illness, crown prince Muhammad al-Badr led a pro-Soviet party and communist activity increased. When the Imam returned in 1959, brutal repression ensued and communists were expelled.
