For decades, prosecutors say, Johann (John) Breyer had successfully eluded a dark past. 

In his twilight years, the 89-year-old Philadelphia man was forced to defend himself against accusations that he was more than a mere perimeter guard at the notorious Auschwitz camp, where more than 1 million people, most of them Jews, were killed during World War II. He maintained that he never persecuted anyone. 

In 2003, a U.S. court ruled that he was not responsible for joining a Nazi unit because he was only 17 years old at the time. 

But new evidence has emerged, U.S. and German prosecutors say, that shows Breyer had to have been involved in the crimes that occurred in that place. 

Breyer, who has lived in the United States since the 1950s, is facing possible extradition to Germany following his arrest Tuesday in Philadelphia, authorities said. 

Federal Magistrate Judge Timothy R. Rice on Wednesday ordered him held without bail, pending an extradition hearing in late August. 

"Extradition is traditionally a very long and complicated process," CNN legal analyst Jeffrey Toobin said. "It's always possible to fight extradition. It just often takes a long time." 

German authorities alleged that Breyer served in the Nazi "Death's Head Guard Battalion" from 1943 to 1945 at the Auschwitz II-Birkenau concentration camp and at another location, according to court papers. 

German authorities have charged Breyer with complicity in the murder of more than 216,000 European Jews from Hungary, Germany, and Czechoslovakia, who were forcibly deported to Auschwitz, in southern Poland, on 158 trains between May and October 1944, according to court documents filed in the U.S. District Court for the Eastern District of Pennsylvania. 
How old was he when he joined?
he was only 17 years old at the time.