Eiss lived in Switzerland, which was neutral during World War II, and was therefore able to serve as the link between people living in countries under Nazi occupation and residents of the free world. He transferred information and requests for help to the Agudath Israel offices in London, New York City, and Istanbul, and facilitated the transfer of money, passport photographs, and requests to locate family members into Europe. He received hundreds of letters from Nazi-occupied countries and was one of the first to obtain a clear picture of the atrocities that were being carried out there .