Military personnel who take part in intense periods of second language (L2) training are at risk of losing their second language skills during periods of underutilization. Cycling between immersion and disuse often requires that personnel refresh their skills anew. This paper describes a research effort aimed at maintaining language skills through a deeper understanding of L2 attrition and the implications for the creation of a game-based intelligent training system for L2 retention. Our goal is to promote L2 retention at the conclusion of formal classroom instruction using serious games operating on portable devices. We describe two aspects of the effort: (i) L2 attrition research results and the implications for training systems and (ii) the development of a proof of concept prototype that illustrates the overall L2 retention system. The L2 attrition results include a descriptive delineation between acquisition and retention and identify the critical language skills most at risk during disuse. These inform our portable games, both in terms of language content and game features such as multimedia and multiplayer competition. The system is designed to promote retention for L2 training such as an Iraqi Arabic language course taught by the US Army at Ft. Irwin.