Singapore has always been vulnerable due to its strategic location and lack of natural resources, relying on trade. In the 1960s, political instability and the spread of communism in Southeast Asia threatened Singapore's security. After independence in 1965, Singapore only had a small military force and needed to build up its defense to protect itself and attract foreign investment. National Service was introduced in 1967 to conscript males for military training. Citizen soldiers and cooperation with other countries helped strengthen Singapore's defense. By the mid-1970s, Singapore had established air, sea, and land forces despite initial challenges.