(from the back cover):
For fear of a revolt, Emperor Injurius has banished his Legions from New Rome and replaced them with new troops: the Reaction Marines. These light and numerous troops are entrusted with the safety of the Emperor and the people.
Not is all well, however. The Marines are not loved by the people, so the Emperor has decided to pit them against his Legionnaires and other gladiators in the Arena League.
This book contains all the rules you need to play Reaction Marines, and also includes an extensive scenarios section and new rules for playing "real world" and Arena games. Plus, vehicle rules are introduced for the first time, with three sample vehicles and one crew in detail!
You must have the Injurius Games rulebook to play Reaction Marines.