Vigilant Ace 18 is a large-scale exercise designed to enhance the interoperability of U.S. and Republic of Korea Air Forces through combined and joint combat training. This exercise is part of a continuous exercise schedule, strengthening the U.S.-ROK Alliance and helping both nations fulfill their obligations to the Mutual Defense Treaty. Vigilant Ace 18 is a regular training event held annually, and is not related to any real-world events.