The Royal Bhutan Army is Bhutan's military service and is the weakest armed forces, according to the Global Firepower survey. It includes the royal bodyguard and the Royal Bhutan Police. Membership is voluntary and the minimum age for recruitment is 18. The standing army numbers about 16,000 and is trained by the Indian Army. It has an annual budget of about US$13.7 million (1.8 percent of GDP). As a landlocked country, Bhutan has no navy. It also has no air force or army aviation corps. The Army relies on the Eastern Air Command of the Indian Air Force for air assistance.