In territories which have remained under their control, metropolitan states have often stationed troops, paramilitary officers, and weapons. Military presence is an affirmation of sovereignty, and troops can ward off real or perceived dangers of foreign attack or irredentist expansion by neighbouring states. They patrol territorial waters and the exclusive economic zones off coasts, and curb contraband, drug-smuggling, illegal immigration and terrorism. These actions have taken on added importance in small territories which lie in the vicinity of large and more powerful states and possess permeable land or maritime frontiers. Troops can also be used, if necessary, to quell insurrection and, less dramatically, to provide assistance following natural disasters. Moreover, military forces use overseas territories as training-grounds for war games and combat practice, and certain detachments – the French and Spanish Foreign Legions – have their major bases there.

Portugal, which withdrew its soldiers from Macao in 1975, provides one exception to the general rule of countries maintaining garrisons in dependent territories. The Dutch and British military presence in their West Indian islands is certainly minimal, but a thousand British soldiers are stationed in the Falklands, several thousand Spanish soldiers in Ceuta and Melilla, many thousands of French troops in the DOM-TOMs, and tens of thousands of US service men and women in outposts such as Guam and Vieques (Puerto Rico) and on bases which the United States has leased from Britain.