The atmosphere of suspicion that beset the 30,000 Jewish immigrants from the Russian Empire living in Paris during the ten years preceding the First World War temporarily improved in August 1914 thanks to the strong wish of the immigrants to serve the country that welcomed them and the number of those who enlisted. However, this was a short-lived respite as grudges from non-commissioned officers, bullying, compulsory service in the Foreign Legion only, and death sentences following the 1915 rebellion dissuaded Jewish immigrants from enlisting. Based on a study of mainly press sources as well as reports of municipal council meetings, the paper shows the reappearance and operation of anti-Semitic xenophobia.