Back in 2001 Defence Alliance for UT99 was released, which was about co-operative play versus AI driven monsters. The mod was so successful, it was obvious that there should be a successor for the new technology.

In early October 2005 DA2 had its first release for UT2004. Many players experienced the new gameplay changes. This introduced the classic Assault mode, where one team is attacking and the other one defending.

As well as the full range of personal weapons, players also have the ability to build additional defences, such as different types of gun turrets. The mod features six different classes: Medic, Mechanic, Anti-armor, Machine Gunner, Sniper and the Rifleman, each with their own special abilities.