Snipped from London Times:

Ratzinger’s past includes brief membership of the Hitler Youth movement and wartime service with a German army anti- aircraft unit. (…) Ratzinger was enrolled in an anti-aircraft unit that protected a BMW factory making aircraft engines. The workforce included slaves from Dachau concentration camp. Ratzinger has insisted he never took part in combat or fired a shot — adding that his gun was not even loaded — because of a badly infected finger. He was sent to Hungary, where he set up tank traps and saw Jews being herded to death camps.

On the other hand pope Jean Paul II took part in anti-Nazi theatre performances in his native Poland and in 1986 he became the first pope to visit Rome’s synagogue.

To read more about this , here’s a direct link to the article from London Times, pretty interesting in my opinion.