It begins, as war movies should, with a battle. The Romans are subduing the last tribes of Germania. By some standards the bloodshed is almost restrained. Restrained, that is, by the standards of action movies. Restrained mostly because it's over quickly.
Death rides in on a very swift horse.
It's a fateful decision. Before it can be made widely known, Commodus kills Aurelius, thereby becoming emperor, and orders Maximus, and his family, killed. Maximus, who has been delivering death to others for years, knows how to cheat it. He wins a number of battles as a gladiator, usually against ridiculous odds. He becomes, a star, and makes it to the big leagues.