Established in 2007 through a combined effort by the North Atlantic Treaty Organization (NATO) International Staff and the Partnership for Peace Consortium, the Defense Education Enhancement Program (DEEP) supports institutional capacity building (ICB) objectives, such as building defense capacity and interoperability, by providing assistance in modern curriculum development (what to teach), faculty development (how to teach), and institutional support (administration and management) for NATO partner professional military education (PME) schools. This report is intended to inform U.S. personnel, NATO Allies, and other Euro-Atlantic governments of DEEP's status from 2018 to 2020, its opportunities and challenges, and ways the program can be improved. The report features three case studies: Armenia, Tunisia, and Ukraine. Ukraine findings might be of particular interest in light of the Russian-Ukraine War. For ICB practitioners, this report also offers general lessons on how PME can support institutional change, sustainment, and development.