Cardinal Ratzinger ran the Congregation for the Doctrine of the Faith.
'God's Rottweiler'
This Vatican department, a descendant of the Holy Inquisition, protects Church orthodoxy.
The job earned him unflattering nicknames such as "The Pope's Enforcer" and "God's Rottweiler".
He has a reputation for stifling dissent, and one of his early campaigns was against "liberation theology" in Latin America.
Some priests became involved in fighting poverty through social action, but to Cardinal Ratzinger it smacked of Marxism.
As a key aide to John Paul II he had a fearsome reputation, but those who know him say he is gentle and somewhat shy.
http://news.bbc.co.uk/2/hi/europe/4463397.stm