German submarines seriously impaired overseas passenger traffic, immigration numbers plunged. The war made it increasingly difficult for American-based families to maintain contact with their scattered family members behind enemy lines. To address this, HIAS sent one of its operatives to Europe to establish communications. He succeeded in securing permission from the German and Austro-Hungarian High Command for residents of the military zones to write short messages to their families to be distributed by HIAS in New York. HIAS also accepted and delivered messages sent by the zone's non-Jewish population. By war's end, HIAS had transmitted a total of 300,000 communications on behalf of separated families. The Russian Revolution of 1917 – and the following civil war, famine, and pogroms that left about 50,000 Jews dead – created another surge of emigration from the former Russian Empire. HIAS continued to help these immigrants find safe haven despite growing anti-immigration sentiments in the U.S. In 1918 HIAS sent a representative, Samuel Mason, on a mission to Japan, Manchuria and Vladivostok on behalf of thousands of European immigrants stranded in the Far East by the World War and the Russian Revolution. He established HIAS offices and international post offices and succeeded in helping both Jews and non-Jews on their journeys to new homes in the US and other countries. He also established The Central Information Bureau for Jewish War Sufferers in the Far East which worked with HIAS to help Jewish refugees in Shanghai through the end of World War II. Between the years 1909 and 1919, HIAS registered 482,742 immigrants arriving in the U.S. HIAS' Ellis Island Bureau interceded with 28,884 held for special inquiry, of whom 22,780 were admitted based on second hearings, with only 6,104 deported. During this period HIAS facilitated the naturalization of 64,298 immigrants. Between the wars The dislocation and turmoil following World War I led to acts of anti-Semitism throughout the former war zone, especially in Poland, Romania, Russia, and Hungary. While other Jewish agencies, most notably the American Jewish Joint Distribution Committee ("The Joint"), supplied Jews in the affected countries with food, clothing, and medical supplies, HIAS created a worldwide network of Jewish organizations to provide assistance in immigration to the U.S., Canada, South America, Australia, and China. The establishment of HICEM in 1927 proved critical to the later rescue operation that saved thousands of Jewish lives during World War II. HICEM resulted from the merger