AbstractThis article, based on existing studies and on newly available documents from the former Soviet archives, relates one of the most controversial missions in ICRC history, the one entrusted to Woldemar Wehrlin in the Soviet Union between the two world wars. In the absence of diplomatic ties between Switzerland and the Soviet Union, the ICRC's permanent delegate in Moscow — in addition to carrying out activities such as representing the ICRC in its dealings with the Soviet Red Cross, liaising with the Nansen mission, ensuring the repatriation of the remaining German and Austro-Hungarian prisoners of war and tracing those gone missing — was also led to defend the interests of his country of origin and fellow countrymen. Although the result of this exceptionally long mission, often called a “quasi-consular” one, was very positive for Switzerland and the Swiss community in Russia, it was more ambiguous for the ICRC, whose image was considerably tarnished by the issue of the organization's relations with the Swiss Confederation.