Until World War II, the United States remained a bit player in Asia, where the European powers had apportioned themselves spacious colonies and spheres of influence. The United States had arrived late on the colonial scene with the Spanish-American War of 1898, which netted it Puerto Rico, the Philippines, and Guam, and, the month the war ended, it annexed Hawaii. The following year, the United States, now a rising power with great power aspirations, made a major foreign policy pronouncement, the Open Door Policy, which strongly suggested that all powers should respect China’s territorial integrity and not attempt to carve out exclusive zones. The other powers had reacted to Chinese political and military incompetence in the First Sino-Japanese War with a postwar feeding frenzy, the so-called scramble for concessions, when they had vivisected China into a welter of exclusive spheres of interest. Americans, as usual, wanted markets open to trade, and exclusive zones threatened this plan. Americans also believed that exclusive zones threatened Chinese interests.

For better or for worse, the ideas of free trade and free access underlying the Open Door Policy have remained consistent themes in American foreign policy ever since. The policy contained an assumption, which Americans did not consider necessary to state because they assumed it to be obvious to all. This was freedom of the high seas, which were assumed to be a commons for all to use up to a few miles from the shore. These two principles, free trade and freedom of navigation, underlie the outlook of a maritime power, but not necessarily of a continental power, which may consider seas as territory to be claimed, divided, and closed off. The Western order of global trade, however, depends on freedom of the seas. The whole edifice crashes down without it.