[166] Americans and other westerners in Peking were besieged and, in cooperation with other western powers, McKinley ordered 5000 troops to the city in June 1900 in the China Relief Expedition.[167] The westerners were rescued the next month, but several Congressional Democrats objected to McKinley dispatching troops without consulting the legislature.[166] McKinley's actions set a precedent that led to most of his successors exerting similar independent control over the military.[167] After the rebellion ended, the United States reaffirmed its commitment to the Open Door policy, which became the basis of American policy toward China.[168]

Panama canal
Closer to home, McKinley and Hay engaged in negotiations with Britain over the possible construction of a canal across Central America. The Clayton–Bulwer Treaty, which the two nations signed in 1850, prohibited either from establishing exclusive control over a canal there. The war had exposed the difficulty of maintaining a two-ocean navy when the Navy had to sail all the way around South America to reach the Pacific.[169] Now, with American business and military interests even more involved in Asia, a canal seemed more essential than ever, and McKinley pressed for a renegotiation of the treaty.