This July 28, 2014, photo shows Jakob Denzinger's portrait on the tombstone of his empty grave in Cepin eastern Croatia
MARTIN HARTMANN
Hartmann is one of the most recent suspects to leave the U.S.
He volunteered for the SS in 1943 and was assigned to one of the Death's Head battalions. Those were the units that ran the Third Reich's system of death and concentration camps.
He served as a guard at the Sachsenhausen concentration camp outside Berlin.
He was stripped of his U.S. citizenship in 2007 after reaching an agreement with the Justice Department. In the agreement, he admitted to his Nazi past even though records obtained by the AP showed he disclosed his service to American authorities before he entered the United States.
Hartmann, 95, lives in Berlin.
JAKOB DENZINGER
In 1942, at age 18, Denzinger began serving in a Death's Head unit. He was posted at several camps, including the Auschwitz death camp complex in occupied Poland.
He settled in Ohio after the war and became a successful plastics industry executive.
Years later, the Justice Department uncovered his past. In 1989, as U.S. prosecutors prepared their case to strip Denzinger of his citizenship, he fled to Germany. He later moved to Croatia.
Denzinger, 90, refused to discuss his past with an AP reporter. "I'm not interested," he said.
MARTIN BARTESCH
Bartesch was working as an apartment building janitor when U.S. authorities uncovered incriminating evidence: As a guard at the Mauthausen concentration camp in Austria, Bartesch had shot and killed a French Jew.
Bartesch feared "financial ruin," according to his family, who denied he had done anything wrong at Mauthausen. He signed an agreement to leave the U.S.
He traveled to Austria in 1987 on a valid passport. Two days after landing, under the terms of the deal, his U.S. citizenship was revoked.
The U.S. refused the Austrian government's demands to take him back. The attorney general at the time, Edwin Meese, eventually apologized to Austria.
ARTHUR RUDOLPH
Rudolph, one of the Germany's most prominent rocket scientists, was brought to the U.S. after World War II because of his technical skill.
But Rudolph signed a settlement agreement with the U.S. in 1983 following an investigation into his use of slave laborers at a Nazi rocket factory.
Rudolph traveled on his U.S. passport to West Germany in 1984. Then he went to the U.S. General Consulate in Hamburg and renounced his citizenship.
The West German government protested, but Rudolph remained there.
He was eventually granted German citizenship and collected U.S. Social Security benefits until his death in 1996.
JOHN AVDZEJ
The Nazis installed Avdzej as a regional mayor in occupied Belorussia, where he aided the Germans in the arrest and execution of thousands of Jews.
When he immigrated to the U.S., Avdzej said he'd been a farmer and tradesman in Poland during the war.
But when the Justice Department uncovered evidence about his role as a Nazi collaborator, Avdzej agreed to leave and renounce his U.S. citizenship.
Embedded in the agreement was a provision that stated "there is no basis under U.S. law for limiting in any way Avdzej's receipt of Social Security benefits."
Avdzej arrived in West Germany in 1984. The West German government protested, but he stayed. He died in 1998 at 93.
WASYL LYTWYN
Lytwyn served in a Nazi unit that took part in the destruction of the Warsaw Ghetto in 1943 — an assault that killed as many as 13,000 Jews.
But when he immigrated to the U.S. in 1957, he denied any affiliation with the .
He found work as a shipping clerk in Chicago.
Lytwyn agreed to leave the United States in 1995 after he admitted that he concealed his service. The settlement agreement stated his Social Security benefits would not be affected.
Lytwyn, 93, is believed to living in Ukraine.
PETER MUELLER
Peter Mueller was born in Yugoslavia but his service as a Nazi SS guard won him German citizenship.
Mueller immigrated to the U.S. in 1956 and settled in Skokie, Illinois.
Then the Justice Department caught up with him.
Mueller admitted he served as an SS guard in the Natzweiller concentration camp in France, watching over prisoners who worked in a stone quarry and in an underground mine.
He voluntarily returned to Germany 1994. Mueller, 90, lives in a nursing home in Worms, Germany, according to family members.
Source: Investigative case files, court and government records, historical documents, and AP research and interviews.