Just picked up the game and it is an excellent what-if the Japanese and the Americans had battled it out in the Pacific in the 1920's. The quality of the game series continues to shine. Thanks MJ12 for the Naval games.

Here is a brief overview; Plan Orange was the U.S. Navy's contingency plan in the event of war with Japan. First developed following the First World War, when Japan was identified as the most likely naval opponent in a future war, the plan assumed that Japan would quickly seize control of most of the Philippines. The U.S. Navy would then launch a counteroffensive across the Mandates in the central Pacific with the goal of relieving Manila and blockading Japan. The plan was continually updated to reflect shifting alliances, improvements in naval technology, and the relative strengths of the fleets.

Quoted from this webpage: http://pwencycl.kgbudge.com/P/l/Plan_Orange.htm