In February 2009, the Institute for Creative Technologies (ICT) at the University of Southern California was contracted to develop a training system for Soldiers and Marines. The goal of the training system was to reduce the number of casualties caused by improvised explosive devices (IEDs). Over the next five months, a team at the ICT responded by drawing on subject-matter experts' input, findings from cognitive psychology, and cinema-style script-writing. The result is the Mobile Counter-IED Interactive Trainer (MCIT), a narrative-focused, mixed-media training simulator that can be deployed anywhere in the world. This paper details the course of MCIT's development, from initial concept to working prototype to finalized training system. We also discuss the technical challenges of developing in Virtual Battlespace 2 (VBS2) and the changes driven by user feedback throughout the development process.