focused on providing support to echelons at the CCMD level and below and may not encompass the full scope of the CSA’s mission. Budget The United States has the world's largest military budget. In the fiscal year 2019, $693 billion in funding were enacted for the DoD and for "Overseas Contingency Operations" in the War against Terrorism. Outside of direct DoD spending, the United States spends another $218 to $262 billion each year on other defense-related programs, such as Veterans Affairs, Homeland Security, nuclear weapons maintenance and DoD. In FY2016 $146.9 billion was allocated for the Department of the Army, $168.8 billion for the Department of the Navy, $161.8 billion for the Department of the Air Force, and $102.8 billion for DoD-wide spending. By function, $138.6 billion was requested for personnel, $244.4 billion for operations and maintenance, $118.9 billion for procurement, $69.0 billion for research and development, $1.3 billion for revolving and management funds, $6.9 billion for military construction, and $1.3 billion for family housing. Personnel The U.S. Armed Forces is the world's third largest military by active personnel, after the Chinese's People's Liberation Army and the Indian Armed Forces, consisting of 1,359,685 servicemembers in the regular armed forces with an additional 799,845 servicemembers in the reserves as of 28 February 2019. While the United States Armed Forces is an all-volunteer military, conscription through the Selective Service System can be enacted at the president's request and Congress' approval, with all males ages 18 through 25 who are living in the United States are required to register with the Selective Service. Although the constitutionality of registering only males for Selective Service was challenged by federal district court in 2019, its legality was upheld by a federal appeals court in 2020. As in most militaries, members of the U.S. Armed Forces hold a rank, either that of officer, warrant officer or enlisted, to determine seniority and eligibility for promotion. Those who have served are known as veterans. Rank names may be different between services, but they are matched to each other by their corresponding paygrade. Officers who hold the same rank or paygrade are distinguished by their date of rank to determine seniority, while officers who serve in certain positions of office of importance set by law, outrank all other officers in active duty of the same rank and paygrade, regardless of their date of rank. In 2012, it was reported that