The Defense Environmental International Cooperation (DEIC) program has been a tool for the Office of the Secretary of Defense and the geographic Combatant Commands (CCMDs) to use as part of their security cooperation engagement activities with other nations. The projects DEIC has supported focus on defense-related environmental themes, with special priority on projects that promote mission sustainment, innovative approaches to environment, safety and occupational health (ESOH) risk management, and building capacity for strategic partnerships. The author has provided programmatic and research support to the DEIC program since its creation in Fiscal Year (FY) 2002. The last year of DEIC funding was FY18. This document reviews the history of the DEIC program and its accomplishments, including its final year of execution.