The immediate military situation
After the surprise attack on Pearl Harbor, the United States was in a precarious military position. The attack severely damaged the American Pacific Fleet, and the Japanese held control of much of the Pacific Ocean. Many believed that the United States would be unable to retake these areas, and some even feared that Japan would invade the mainland United States. In this context, the decision to attack Japan was seen by some as a necessary defensive measure.
The long-term strategic implications
The attack on Pearl Harbor was also seen by some as a strategic move to prevent Japan from gaining further control over the Pacific Ocean and to preserve American influence in the region. By attacking Japan, the United States hoped to slow the Japanese advance, give itself time to rebuild its military, and eventually retake the Pacific islands that had been lost.
The moral and ethical considerations
Whether or not the attack on Pearl Harbor was morally and ethically justified is also a complex question. Some argue that the attack was a necessary response to Japan's aggression, while others believe that it was an unjustified act of war. The decision to attack Japan after Pearl Harbor was a controversial one, and it continues to be debated today.