Stealth was essential because Kido Butai could not risk a surface battle

Japanese planners charted a northern approach away from normal traffic, aiming to reach Hawaii without warning the defenders. The strike would attack airfields as well as the fleet, reducing the base's ability to defend itself or strike back. Avoiding discovery also protected the carriers from a surface encounter while bad weather prevented them from launching aircraft. A hypothetical meeting with North Carolina and Washington, accompanied by cruisers and destroyers in a storm, illustrates that danger. The Japanese force had no attractive way to fight those battleships under such conditions. Merchants, patrol aircraft, and submarines therefore all posed risks to the approach.