1. Rising Tensions in the Pacific: Throughout the late 1930s, Japan's military expansions into China and other parts of Asia created growing concerns in the United States regarding Japan's intentions in the Pacific. 2. Increased Military Installations: The U.S. fortified military installations in Hawaii, particularly at Pearl Harbor, in anticipation of possible conflict, which heightened Japanese frustration towards the U.S. presence. 3. Diplomatic Signals: Japan's aggressive posturing was evident through its diplomatic communications, which, although monitored, were often not shared in a timely manner with military commanders in the field. 4. Japanese Defense Preparations: Leading up to the attack, Japan conducted both military and intelligence operations, including the coordination of forces and preparations for a surprise offensive in the Pacific. 5. Notable Military Incidents: Prior skirmishes in regions such as Guam, Wake Island, and the Philippines signaled Japan's readiness for war and established a pattern of aggression. 6. The Surprise Attack: On December 7, 1941, Japan orchestrated a well-planned, surprise attack on Pearl Harbor, which initiated the United States' entry into World War II and had far-reaching consequences on international relations.