 This, and other successful hit-and-run raids by American carriers in the South Pacific, showed that they were still a threat, although seemingly reluctant to be drawn into an all-out battle. Yamamoto reasoned that another air attack on the main U.S. Naval base at Pearl Harbor would induce all of the American fleet to sail out to fight, including the carriers. However, due to the increased strength of American land-based air power on the Hawaiian Islands since the December 7 attack the previous year, he judged that it was now too risky to attack Pearl Harbor directly.
