This lesson is designed to explain the causes of World War I in a clear and easy to remember way with an acronym and graphic organizer. A customizable Powerpoint is included that you can edit to fit the needs of your class, as well as a graphic organizer. I designed this lesson in response to a student comment that whenever he asked an adult why this war started, the only answer he got was "it's complicated." It is, but with this lesson my students have been able to grasp the major concepts and write a follow up essay analyzing which of the four causes was most critical in starting the war. This lecture follows an in-class simulation where students experience the four "MAIN" causes and attempt to use diplomacy to prevent the outbreak of war.