From a Washington Post obit by Michael S. Rosenwald headlined “Allan A. Ryan, who hunted down Nazis hiding in America, dies at 77”:

Following World War II, thousands of Nazi collaborators masquerading as war refugees immigrated to the United States with new identities. They worked as farmers or butchers or assembly-line workers. Some had fenced-in backyards.

Allan A. Ryan hunted them down.

Mr. Ryan ran the U.S. Justice Department’s Office of Special Investigations, a unit designated to find and expel anyone in the United States who had assisted the Nazis. During his tenure from 1980 to 1983, Mr. Ryan and his team followed leads around the world, including taking depositions of witnesses in the Soviet Union.