Afghanistan became a member of the United Nations in 1946. Historically, Afghanistan had strong relations with Germany, one of the first countries to recognize Afghanistan's independence in 1919; the Soviet Union, which provided much aid and military training for Afghanistan's forces and includes the signing of a Treaty of Friendship in 1921 and 1978; and India, with which a friendship treaty was signed in 1950. Relations with Pakistan have often been tense for various reasons such as the Durand Line border issue and alleged Pakistani involvement in Afghan insurgent groups.