The Boxer Rebellion
America's growing involvement in Asian affairs received added impetus from the Boxer Rebellion of 1900. The United States had already espoused the Open Door policy, proclaiming the principle that all nations should share equally in trade with China. China's exploitation by foreign nations aroused resentment among young Chinese, who formed a secret society called the "Righteous Fists of Harmony" or Boxers.
With the connivance of the Dowager Empress, the Boxers launched a bloody campaign to rid the country of foreigners who, fearing for their lives, took refuge in their legations in Peking. The legations, defended by small numbers of soldiers and armed civilians, were soon besieged by a much larger force of Boxers and Chinese imperial troops.
Because it already had substantial forces in the Philippines, the United States contributed a sizable contingent to an international relief force sent to China. A signal detachment of four officers and nineteen men under the command of Maj. George P Scriven accompanied the American troops on their march to Peking in August 1900. These men, in conjunction with British signal personnel, constructed a telegraph line to accompany the advance of the allied army from Tientsin to Peking, a distance of about ninety miles.
The allies entered Peking on 14 August and saved the beleaguered legations. For several days the British-American telegraph line provided the only means of communication between the city and the outside world. During the period of occupation that followed, additional Signal Corpsmen arrived to construct a permanent telegraph line between Peking and Taku, on the coast, a distance of 122 miles. The occupation troops withdrew from China in September 1901, but a small American force remained to guard the Tientsin-Peking railway in accordance with the Boxer protocol.
Find out more in "Getting the Message Through" at http://www.history.army.mil/books/30-17/Front.htm#toc