In modern terms, a militia is a group of citizens organized to provide a paramilitary service. The word "militia" can have other implied meanings. The most common three being:
(1.) The entire able-bodied population of a community or state, which can be called to arms against an invading enemy (Such was the case in the early Americas and is still part of the US Constitution).
(2.) An official or unofficial reserve army composed of volunteer citizen soldiers used for defense or law inforcement, most often under Marshal Law.
(3.) And in more modern time the press uses the term to describe a private non-governmental force not supported or sanctioned by their own government.
A militia can serve to supplement the regular military or it can oppose it; for example a militia could resist or support a military coup. In some circumstances, the enemy against which a militia might be mobilized could be the domestic political opponents of a government or its own government. It is this potential role that causes militias to be so controversial and often openly opposed.
Thus, the word militia can have either a good or a bad connotation depending on ones point of view. In the contemporary United States, the easiest way to identify a loyal (or good) militia is their conformity to the following:
(1.) All members take and sign an oath to defend the Constitution and to abide by the laws of all Federal, State and local governments of the United States.
(2.) The command and bylaws of the organization recognize that all "Constabulary Powers" are derived from the duly appointed officials of the responsible governing agency, which they may from time to time support and/or assist.
Most Americans are in the U.S. Militia and do not know it. For example: United Sates Code, Title 10, Chapter 13, Section 311 - The militia of the United States consists of all able-bodied males at least 17 years of age and except as provided in section 313 of title 32, under 45 years of age who are or who have made a declaration of intention to become citizens of the United States and female citizens of the United States who are commissioned officers…
HISTORY - The “Regular Army” of the United States, a permanent force maintained during war and peacetime, became the Regular Army during the American Civil War (1861-1865). The term was used to describe the small contingent of U.S. Army soldiers who served in the Union Army side-by-side with the massive State militias and volunteer forces.
Officers during the Civil War were known either by the rank suffix "of Volunteers" or if Regular Army, by the rank suffix "USA". A regimental Colonel would be identified as "Colonel of Volunteers" while a Regular Army Captain would be identified as "Captain, USA". Regular Army officers during the Civil War could accept commissions in volunteer forces and be granted brevet ranks; a rank higher than their permanent USA commission.
In some cases, officers held as many as three ranks; a rank in the Regular Army, a rank of Volunteer Forces, and a brevet rank as the result of battlefield promotion. These officers typically referred to themselves by the highest rank obtained. After the Civil War ended in 1865, the term Regular Army was used to denote an officer's permanent rank when a brevet commission had also been received. If no brevet rank was held, the officer was simply referred to by their USA or permanent rank. All enlisted personnel, except those who received brevet commissions, were considered simply United States Army.
Prior to 1918, the Army was a single entity known as the "United States Army". During the First World War, the "National Army" was founded to fight the European conflict. A career soldier was known only as Regular Army. Units were augmented by the "Enlisted Reserve Corps" (ERC) and the "Officer Reserve Corps" (ORC) that filled billets as needed.
The U.S. Army was founded in 1920 when the large drafted force of the National Army was demobilized and disbanded. The ORC and ERC became the U.S. Army Reserve. Throughout the 1920s and 30s, the Regular Army was badly underfunded and understaffed ranking sixteenth in the armies of the world. By the early 1930s, the "State Guards" began to build up with limited assistance from the Federal government.
In 1941, the Army of the United States was founded to fight the Second World War. This gave rise to the first combined Army components under unified commands. After World War II, the ORC and ERC were integrated back into the Army Reserve. The U.S. Army still remains divided into the Regular Army and the Army Reserve.
The United States National Guard is an armed force under the command of the individual state governments. Prior to the 21st century, members of the National Guard were considered state employees unless federalized by the U.S. Army in which case the National Guard members became members of the Army Reserve. Currently, all National Guard members hold dual status.
Various State Defense Forces (volunteers) also exist, sometimes known as the State Guard are authorized under Federal Law. In some states, the State Guard serves as an auxiliary to the state’s National Guard. Some anti-gun proponents argue that this is what the founders of our constitution were referring to in the phrase “under a well regulated militia”. However, most State Guard units remain unarmed and only private citizens are currently permitted to “keep and bear arms”.
Except in times of extreme national emergency, such as a mainland invasion of the United States, the State Guards and lawfully formed militias operate independent of the U.S. Army and are not seen as a component of an armed military. The organized unarmed paramilitary militia units of the United States perform volunteer duties and honor guard services. Some trained units work with the State, Federal and local governmental agencies in disaster relief and many are viewed as a valuable reserve force willing to assist in times of local or national emergencies.