Verified answer

They acted in a way that violated the rules that they were supposed to obey. Literally, it refers to people that were forced to live on reservations and were not permitted to leave or establish residence elsewhere. It is used as a metaphor meaning a total violation of the rules that apply to the person. Going off the reservation carries the idea of doing illegal actions, although it does not require lawbreaking, just ignoring policy is often enough to be seen as having gone off the reservation. Doing what you have been specifically told not to do, is the basic idea.

It means when you screw a girl of a different race . . . or at least finger the hole.

Out of bounds.

And yeah, the etymology is racist, meaning native Americans were barred legally by govt from literally leaving the reservation. Like segregation, with giant pens.

It does NOT literally mean to leave an area. I don't know where people got that idea. The others are right that it means violating the rules, or doing what they thought would work rather than following standard policy.

DR +Mrs has the Only correct answer.

If the two soldiers "went off reservation", then that means that the two soldiers were not supposed to leave to go find their fellow soldier. They were doing something against their superiors orders but it resulted in a good thing happening.

the phrase is "gone off THE reservation"... It means that they did something unusual, out of the ordinary, unexpected, contrary to standard procedure.

Freelancing. Not following orders or procedure.

The soldiers had left the area they were supposed to be in.