South Yemen's withdrawal from an active support role for insurgency in neighboring states resulted in a shift to what Aden's leaders regarded as another revolutionary strategy: active membership in a regional pro-Soviet bloc. Such a bloc is based on an agreement among its members, and between them and the Soviet Union, to cooperate in achieving strategic and ideological goals. This is not necessarily a rigid format; the members of the bloc may possess considerably more tactical flexibility and maneuverability than they would as participants in a formal alliance, and relations among individual member-states may become convoluted.