Tour of Duty is the second game in the Squad Battles Series and continues from the original game Squad Battles Vietnam. In addition to over 40 scenarios, Tour of Duty has a Campaign Game, the first in the Squad Battles series to do so, which enables the player to assume the role of a leader and fight multiple battles over the course of a year in Vietnam. There are 5 campaigns, including American Army, Marine, Air Cavalry, Army Riverine, and Australian forces. source - http://www.hpssims.com/Pages/products/SB/TOD/TOD.html