The battle is somewhat accurate. But that's about it.

The movie implies De Gaulle was directly involved in sending troops to counter the UN. That's just speculation.

It makes out the fighters to be former (that's unclear) French legionnaires, when they were mostly Belgian mercenaries.

The character of general McEntee is pure fabrication. The commander of the UN forces in the Congo at that time was General Sean McKeown, a highly regarded general at the time. In the movie, he is portrayed as a weak man with little involvement or power. Not sure how they got away with that as it's borderline defamatory.

The filmmakers also conveniently chose to leave out that Dag Hammarskjöld's (UN Secretary General) plane was shot down over Rhodesia. It is believed that it was shot down by the British.

Britain's involvement in the events is seriously downplayed. In fact, there isn't a single mention in the entire film of British presence and power in that part of the world.