The outbreak of World War I in 1914 brought the largest influx of Jews from Eastern Europe to date: 138,051 in that year alone. However, when the North Atlantic became a battle zone and 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.