In June 1219 Danish crusaders fought a vicious battle against local pagan warriors at the place in northern Estonia where Tallinn now lies. The battle-known then as the Battle of Lyndanise-was a narrow victory for the crusaders and eventually turned out to be a pivotal event in the national histories of both Denmark and Estonia as a milestone in the overall military conquest of the entire region by (mostly) western military powers. The main scope of this book is to present a study of this military conquest of Estonia around 1200 with a special focus on the Scandinavian involvement, enabling us to better understand the intense political, military, and religious changes that came to influence the region and its many people from the early high medieval period onwards.