The failure of the Boxers allowed the various European & Japanese imperialists to expand their territorial franchises over the next decades and further weaken the Imperial control. Unlike the others, the United States claimed no ports but did participate in gaining most favored nation treatment to allow its US Navy to patrol and conduct anti-piracy missions on the Yangtze River from the 1860s and on.
A decade after the Boxer Rebellion, the Qing Monarchy fell to a coalition of ad-hoc regional warlords and western-influenced radicals (1912). Putative leader of this movement was Dr Yat-sen Sun M.D. (Sun Yat-sen), but with the size of China, control was extremely fragmentary. A brief resurgence of the Monarchy in 1915 didn't last but showed the fragility of the newly named "Republic of China" government.
Given the snakepit of regional rivalries and warlords, Dr Sun allied his power base of the China Nationalist Party (Kuomintang [KMT]) with the Communist Party of China and the new Soviet Union and the Communist International (Comintern). Thus his new government had the entire stewpot, warlords to Communists but with the additional power, their armies were able to re-establish control over northern China. In 1923, Dr Sun named General Kai-shek Chiang (Chiang Kai-shek) as the chief of the National Revolutionary Army.
When Dr Sun dies of cancer in 1925, the stewpot boils over and the Yangtze River (longest and most strategic river in China) becomes an ad-hoc boundary and war zone. While the "Sand Pebbles" is fiction, the elements that are included were real. A multi-way battle within China for control made the presence of foreigners an irritant and quite precarious.
Both the Chinese and the sailors were pawns of forces and traditions that were rapidly changing. The cusp part of the novel, the Nanking Event, was, in hindsight, a reprise of the Boxer Rebellion. With warring armies eliminating local government, local populations seize the opportunity to loot hated foreign enclaves which brings foreign naval intervention by artillery and troops. Fun times if you like chaos!
In 1927, future dictator and mass murderer, Zedong Mao (Mao Zedong) (b.1893), got his first prominent role in an armed uprising against the KMT in Hunan Province, the first battle of the Chinese Civil War. By the time of his death in 1976, by execution, imprisonment or forced famine, an educated estimate of 60-65 million Chinese deaths (10% China population) marks him as the greatest(?) murderer in history! FYI: In terms of world population however, no one (yet) has equaled Genghis Khan's (d.1227) record of 11.1% (40 million) from China to Eastern Europe.
Sorry, I got carried away on this reply - fascinating history!
Thank you! I remember reading about one of the warlords who accepted Christianity and baptized whole masses of troops with firehoses...