Which countries were a part of the international force that defeated the boxers? why did soldiers from all of these nations join together to combat the boxers?

On June 20, 1900, the Boxers, now more than 100,000 strong and led by the court of Tzu’u Hzi, besieged the foreigners in Peking’s diplomatic quarter, burned Christian churches in the city, and destroyed the Peking-Tientsin railway line. As the Western powers and Japan organized a multinational force to crush the rebellion, the siege of the Peking legations stretched into weeks, and the diplomats, their families, and guards suffered through hunger and degrading conditions as they fought to keep the Boxers at bay. On August 14, the international force, featuring British, Russian, American, Japanese, French, and German troops, relieved Peking after fighting its way through much of northern China.