When Kennedy was an upperclassman at Harvard, he began to take his studies more seriously and developed an interest in political philosophy. He made the dean's list in his junior year. In 1940 Kennedy completed his thesis, "Appeasement in Munich", about British negotiations during the Munich Agreement. The thesis eventually became a bestseller under the title "Why England Slept". In addition to addressing Britain's unwillingness to strengthen its military in the lead-up to World War II, the book also called for an Anglo-American alliance against the rising totalitarian powers. Kennedy became increasingly supportive of U.S. intervention in World War II, and his father's isolationist beliefs resulted in the latter's dismissal as ambassador to the United Kingdom. This created a split between the Kennedy and Roosevelt families.