Global defense analyst Robbin Laird brings you, "Defense XXI". This compendium of articles published in 2021 provides an overview of several key trends and themes regarding the evolution of U.S. and allied defense. We have focused on several key developments during the year in the defense domain which will have longer term impacts in the years ahead. During 2021, we visited several U.S. Naval and Marine Corps bases, as well as France and Poland as well as "virtually" Denmark and the United Kingdom. During those visits, we interviewed many senior commanders about how they are focused on shaping a more effective military to deal with the evolving challenges from the authoritarian powers. As former Secretary of the USAF, Michael Wynne commented: "The articles in the book, organized as they are by natural topics, will undoubtedly enhance the reader’s understanding as to just how weapons and information technology and the distribution and relationship knowledge have affected and impacted the age old concept that military action is simply an extension of diplomacy by other means."