Secrecy, range, and protection define the strike

The approach had to avoid major shipping routes because a merchant ship could report the Japanese force. Radio equipment was uneven, but a modern freighter or liner still posed an avoidable risk of discovery. Taking six valuable carriers also required enough protection to escape an accidental encounter with American forces exercising near Hawaii. The carriers were needed for subsequent operations, so losing them would undermine the larger strategy. Surprise was principally a means of buying time to inflict maximum damage on an unprepared fleet. The force therefore needed sufficient range and striking power as well as a credible way to return.