What is the military term for fighting the enemy without permission?

What is the military term for fighting the enemy without permission?

'Insubordinate conduct' is the term given to disobeying orders but this is too general as it can mean failing to carry out an order to do something.

What I'm looking for is a term that has similar connotations as 'vigilantism' but in a military context. Similar connotations meaning trying to take affairs into one's own hands - but in this case in a military context.

I thought of militancy but that word is usually used to describe people who fight against their own authority / government - not against the common enemy ......

Unauthorized engagement (of the enemy) is the term I would use.

Fighting the enemy in military terms is frequently referred to as engaging the enemy. Without permission, it would be an unauthorized action.

Vigilantism could be applied to this sort of action, too. But, I agree that usually comes with a sense of justice attached to it.

Going off the reservation is a common expression (despite it being politically incorrect today). It can mean to engage in disruptive activity outside normal bounds.

Originally, "going off the reservation" literally meant leaving the reservation to which one is restricted.

This article is about the phrase and its usage, including this one:

The CIA agent was not supposed to assassinate those people. When he started killing them, he went off the reservation and had to be eliminated.

Here is an article using the phrase, tying it to insubordination (but not fighting).

This Urban Dictionary definition captures it, as well (ref #2)

Going off the reservation is when certain elements such as spies or assassins either fail to complete an assignment/mission, go on an unauthorized mission, get caught and spill their guts, or go rogue. Usually resulting in the need to neutralize(kill their ass) the said element.

This introduces another term: to go rogue which means operating outside normal or desirable controls.

You can use these phrase like this:

Colonel Smith and one of his companies went off the reservation this morning, supporting the partisans in an attack on the radio station. He may have been colluding with an agent at our forward base outside the city who decided to go rogue with him.

Wildcat would be applicable to this. I think there may be a better word, but I can't think of it right now.

A particular type of this is called filibustering. A filibuster is a private citizen who goes on a military expedition in a foreign country, without his own government's authorization. Governments often make this illegal (it's obviously harmful to friendly international relations when you allow your own citizens to attack a foreign country).

The most famous filibusters were American adventurers who filibustered mainly in Latin America and the Caribbean in the mid-19th century. For example, William Walker raised a force to conquer Nicaragua and made himself President.