Jack's topic for his senior thesis was "British foreign policy and the coming of World War II". He became totally absorbed in the project. His access to public officials, and the aid he was able to receive as the Ambassador's son greatly helped his research. The premise of his thesis was that no one politician was responsible for the unpreparedness of England, rather, it was its political system- a democracy that failed to come to grips early enough with the threat the Nazis posed. The Funk Book Company went on to publish the thesis as a book entitled, "Why England Slept". Much to everyone's surprise, the book achieved commercial success.
Upon his return to the United States, Jack became actively involved on campus with those who worked to support the Allies. This was in distinct contrast to his brother, Joe Jr., who was active in the "America First" movement. Most of Jack's efforts at this time, however, were directed towards completing his Senior Thesis entitled, "Appeasement at Munich: The Inevitable Result of the Slowness of Conversion of the British Democracy from a 'Disarmament' to a 'Rearmament' Policy". The thesis was a complete analysis of the conditions of British politics that led to the decisions at Munich. Kennedy's basic hypothesis was that it was not merely the fault of Chamberlain, but rather the total British political system, that rendered the British unable to respond to the changes in Germany. As a result, the British did not rearm in time. Of course, Kennedy had unprecedented advantages in writing the thesis. He both witnessed the events first hand, and had unique access to the players making the history. Kennedy also had access to the resources of the United States Embassy in London, which sent him whatever materials he needed. His thesis was well-received, but not thought to be outstanding. Kennedy's degree was awarded magna cum laude.
This thesis was destined not to end as "just another senior thesis" for Jacks' father showed the work to journalist Arthur Krock, who agreed to help get the work published. Jack worked with Krock on editing (the extent of which will never be truly known.) Krock convinced his literary agent, Gertrude Algase, to try to sell the book. Krock also suggested giving the book a commercial title and it was renamed, Why England Slept. After a few tries, Algase finally found a willing publisher in Wilfred Funk, Inc. The publisher moved quickly and by July, the first copies were off the press. The book received positive critical reviews and, much to the surprise of all concerned, the book became a best seller. A total of 80,000 copies were sold. As a result, Jack became an instant celebrity. In addition, he earned $40,000 in royalties