What is a militia?

Answer 1

A militia is made up of a group of individuals who are normally civilians, but upon being called together (usually by some political leader) form a military unit for temporary duty. In pre-industrial times, they generally brought weapons from their home to fight with, and generally had very little (if any) formal military training as a unit. In modern times, they are usually equipped by the government, and many have some limited training in the combat arts (i.e. small unit tactics, proper communications protocols, etc.). Modern militias are almost exclusively light infantry, equipped with little more than personal firearms and perhaps light vehicles for transport.

The defining characteristic of a militia is its temporary nature, and that it is filled with persons not normally considered part of the military. Militia units are almost always used solely for homeland defense.

The United States National Guard can perhaps be called a militia, though it receives far more equipment and training (and formal military integration) than virtually any other "militia" organization. More honestly, the National Guard in modern times is really a special-duty military reserve unit.

The Minute Men of the American Revolutionary War were one example of a old-style militia.

In addition to the traditional usage, the word militia is also commonly used today to describe informally organized armed groups who act as the personal "army" of some warlord or other strongman. These groups are little better than armed mobs, with virtually no training other than basic "how to your your gun" instructions. Such militias really are just a step up from an armed gang, having nothing to do with the formal government structure of the country (and, often, in contention with a country's formal military, sometimes to the point of active fighting). Militias in this sense are common in places experiencing extreme civil unrest, including failed states and civil wars. Somalia and Sudan are prime examples where militias in this mold exist.

Answer 2

a group of men

Answer 3

a volunteer military force