This paper presents an analysis of the degrees of preparedness (or lack of) on the part of the United States and its naval forces in reaction to and in anticipation of actions by the Imperial Japanese Navy (IJN) primarily during the interwar period (1918-1941), with analysis of relevant earlier developments. Primary and secondary sources from both the interwar period and post war (post 1945) are utilized. While sources mentioning the unpreparedness of the U.S. in a naval war with Japan are used, sources that dismissed the danger of such a conflict are also utilized to offer the necessary contrast. While there is a wealth of information on the interwar period, World War II, and the Japanese Navy that is easily accessible, the main problem in conducting research was the contrast in detail, events, and exact dates written by each author. Additionally, since only English sources were used, further research making use of Japanese sources is necessary to shed more light on the subject. It was found that the U.S. was not prepared for a naval engagement with Japan. While U.S. president, Franklin D. Roosevelt supported the building of a superior U.S. naval fleet, naval appropriations issued by the U.S. Congress were insufficient. Moreover, to make its case for increased funding, the U.S. Navy used naval information relating to Japan that was inaccurate and little more than rumor. As Japan continued its conquest of China and French Indochina, the U.S. issued embargoes but did not militarily intervene until Japan’s attack on Pearl Harbor on December 7th, 1941. To understand naval affairs in the Asian and Pacific region today, it is necessary to comprehend U.S. naval policy toward the IJN during the interwar period. No other event has influenced Asian and Pacific affairs during this period as significantly as the Pacific War. The complete breakdown of communications between the U.S. and Japan and the resulting naval war offer valuable lessons for policy makers of today.