The Health.mil is the official website of the Military Health System and Defense Health Agency. The Military Health System is one of Americaâs largest and most complex health care institutions, and the worldâs preeminent military health care delivery operation. Our MHS saves lives on the battlefield, combats infectious disease around the world, and is responsible for providing health services to approximately 9.6 million beneficiaries, composed of uniformed service members, military retirees, and family members.