Greetings! I shall attempt to shed some light on the contributions of this fairly under-appreciated and even lesser-known contingent of the First World War, and their origins in the chaos of warlord-era China. So let's begin.

The Republic of China entered the First World War on the side of the Entente Powers on August 14, 1917, though by no means due to its own anti-German sentiment or pro-Entente allegiances. Rather, the decision had been made after a fair bit of political infighting in the halls of the National Assembly, with notable figures such as Duan Qirui and Sun Yat-Sen taking part. For the record, it's interesting to note here that Sun was himself anti-Entente, arguing that British and Russian imperialism had taken more from China than Germany had the past century.^(2) Here's David C. Fawcett on the matter of the Chinese entry to the Great War:

The Chinese did declare war against Germany and Austria-Hungary on 14th August 1917, for reasons of domestic policy and also to ingratiate themselves with the [Entente] Powers and win resources from them which would support a military campaign to reunify the country under Beijing's rule.

The Chinese Army however, was not at all fit to be sent abroad, being caught up in the Warlord Era, where various military cliques and warlords vied for control of the Imperial Throne in Peking. As a result, negotiations had already begun in 1916 between Britain and France to dispatch Chinese labourers to serve on the Western Front. Here's an actual extract from a report about the to-be Chinese Labour Corps from 1920:

"The Chinese Labour Corps, which consisted of [at the time] 94,146 Chinese, was created to release where possible all available man power for the fighting units, and in April 1917 the first ship-load of labourers was landed in France.

Over the course of the war, some 140,000 Chinese labourers would join their fellow countrymen helping out the Entente Powers on the Western Front, performing all manner of duties to support the troops on the frontlines. This obviously meant that they were never sent to the frontlines as proper soldiers, and it's very unlikely that any of them even fired a shot in anger at the enemy, but their contributions were massive nonetheless. They were formed into their own support unit, the massive Chinese Labour Corps (CLC).^(6)

These duties included manning field kitchens, moving supplies between trenches, operating supply depots, unloading cargo ships and trains, build various military structures, lay railway lines, and other such logistical tasks. Even after the war was over, the corps remained at station in France up until 1921 to bury bodies, search shell holes, unearth unexploded bombs, and roll-up barbed wire.

In short, the Chinese Labourers on the Western Front during the First World War assisted in a great many ways to ensure the Entente Powers could keep on fighting their war, and even after Versailles some were still around to help clean up the landscape. I have attached in the sources an excellent article (JSTOR access required) by Brian C. Fawcett which chronicles in-depth the entire "life" of a Chinese Labour Corps member from recruitment, to dispatch, to operations, and repatriation. Further, consider reading the primary source also linked, a report on the CLC from 1920.

Feel free to ask any follow-ups and happy reading!

Sources:

FAWCETT, BRIAN C. "THE CHINESE LABOUR CORPS IN FRANCE 1917-1921." Journal of the Hong Kong Branch of the Royal Asiatic Society 40 (2000): 33-111. Accessed January 10, 2021. http://www.jstor.org/stable/23895259.

Report giving the history of the Chinese Labour Corps used behind the lines in France 1917-19, from the British Library. Accessible here (free).