Some battles last days. Or weeks. When Christian crusaders laid siege on the Mediterranean seaport of Acre late in the 12th century—bent on recapturing the Holy Land from the Egyptian sultan Saladin—they launched a military epic that claimed tens of thousands of lives over two years.

In a discussion of his new book The Siege of Acre, 1189-1191: Saladin, Richard the Lionheart, and the Battle That Decided the Third Crusade, military historian John D. Hosler of the U.S. Army Command and General Staff College analyzes this monumental confrontation, the centerpiece of the Third Crusade. England’s Richard I was one of four kings drawn into a multi-ethnic conflict that engaged forces from Europe, the Middle East, Egypt, and the Maghreb region of North Africa.

For the Presentation slides, click here.