What is Military?

Legal Definition
The military, also called the armed forces, are forces authorized to use deadly force, and weapons, to support the interests of the state and some or all of its citizens. The task of the military is usually defined as defense of the state and its citizens, and the prosecution of war against another state. The military may also have additional sanctioned and non-sanctioned functions within a society, including, the promotion of a political agenda, protecting corporate economic interests, internal population control, construction, emergency services, social ceremonies, and guarding important areas. The military can also function as a discrete subculture within a larger civil society, through the development of separate infrastructures, which may include housing, schools, utilities, food production and banking.

The profession of soldiering as part of a military is older than recorded history itself. Some of the most enduring images of the classical antiquity portray the power and feats of its military leaders. The Battle of Kadesh in 1274 BC was one of the defining points of Pharaoh Ramesses II's reign and is celebrated in bas-relief on his monuments. A thousand years later the first emperor of unified China, Qin Shi Huang, was so determined to impress the gods with his military might that he was buried with an army of terracotta soldiers. The Romans were dedicated to military matters, leaving to posterity many treatises and writings as well as a large number of lavishly carved triumphal arches and victory columns.
-- Wikipedia
Legal Definition
The Constitution grants to Congress the power to raise and support armies and a navy, to suppress insurrections, and repel invasion among other military-related governmental roles. Thus, the main source of legal authority in this area is federal law. Congress's control over formation, organization and government of the national armies is plenary and exclusive.

Military law consists of the Uniform Code of Military Justice and other statutory provisions for the government of persons in the Armed Forces to which may be added the unwritten common law of the usage and custom of military service as well as regulations and authorized by the President as Commander in Chief of the Armed Forces (See 10 U.S.C. ยง 121). It is a part of our body of law as a whole, and is fully recognized by civil courts; it is in force in time of peace as well as in time of war. All persons serving in the Armed Forces of the United States are subject to military law at all times.
Legal Definition
Pertaining to war or to the army; concerned with wav. Also the whole body of soldiers; an army.
See also
-- Black's Law Dictionary
Legal Definition
That which belongs or relates to the army.
-- Bouviers Law Dictionary