The focus and context of the great powers' interest in the Persian Gulf has altered —often subtly, sometimes dramatically —since Britain established its hegemony in the region in the 19th century. Britain engaged in a lucrative trade, but primarily sought to protect imperial communications and the approaches to India. Today, it is oil that gives the region its strategic importance. For a number of years after World War II, Britain remained the paramount power in the area, maintaining maritime peace, handling the external affairs of the Gulf sheikhdoms, mediating local disputes, dominating trade. Since Britain's withdrawal from the Gulf in 1971, the situation has become somewhat more messy.