By late-March, having achieved their initial aims with surprising speed and little loss, albeit against enemies ill-prepared to resist them, the Japanese paused to consider their next moves.
On April 18, in the midst of these debates, the Doolittle Raid struck Tokyo and surrounding areas, demonstrating the threat posed by US aircraft carriers, and giving Yamamoto an event he could exploit to get his way as further debate over military strategy came to a quick end.