As the conflict in Iraq has moved from open combat toward stability and support operations, both sides have reacted to the changing nature of the conflict. This has resulted in an increased need to quickly revise military tactics, techniques, and procedures (TTPs). This need, coupled with the largest rotation of U.S. troops since World War II, has resulted in an increased need and effort to capture and pass along lessons learned to troops rotating into the conflict area. This paper describes the design and implementation of a "lessons learning" game, DARWARS Ambush!, developed under the DARPA Training Superiority Program (DARWARS) and managed by the Office of Naval Research (ONR). DARWARS Ambush! is a computer-based training game that enables squads to experience and respond to ambush situations. Although initially focused on the most common types of ambushes observed in Iraq, those involving convoy operations and improvised explosive devices (IEDs), DARWARS Ambush! is designed to be useful in training for more general operations, such as military operations in urban terrain (MOUT). A primary feature of DARWARS Ambush! is that it allows troops in the field to construct and modify scenarios based on their experiences in order to pass along their hard-won knowledge to other military personnel. The system is being developed as a modification of an existing commercial game, which provides an immersive and compelling experience. This "leveraging" of commercial software is enabling the project to meet its ambitious schedule - development, testing, and deployment within six months.