From the introduction: "5150 Hammer & Anvil is the companion book to 5150 Star Army – 2nd Tour, and can also be used with 5150 Star Marines. Hammer & Anvil is a set of Sci-Fi tank combat rules that focuses not only on the vehicle, but its individual crew members. Hammer & Anvil can be played with any counters, models, or minis you may already have. Play it as a RPG or as a wargame; it’s both." From the rules: "In Hammer & Anvil each vehicle consists of both the vehicle and its crew. Players will usually start with one or two vehicles and work their way up to larger numbers. No matter what size formation you decide to use, the basic starting point is the individual vehicle and its crew."