VATICAN CITY - Pope Benedict XVI on Monday appointed German archbishop Ludwig Muller to head up the Vatican's orthodoxy watchdog, replacing American Cardinal William Levada who is retiring from the post.
The Archbishop of Regensburg in southern Germany, Muller has a reputation as a defender of Catholic Orthodoxy and has been criticised by German groups clamouring for change, such as "Die Kirche von unten" (The Church from below).
A personal friend of the German-born pope, who charged him with publishing his writings, Muller is however also known for his long-standing support for Gustavo Guttierez, founder of the socialist Liberation theology movement.
Muller, 64, takes over at the helm of the Congregation of the Doctrine of the Faith, which plays a key role in the Vatican's governing body, holding the diverse theological initiatives within the global Catholic church to account.
He is expected to take up the post in the next few days when Levada retires.
The watchdog cracks down on dissident factions, from rebellious priests in Australia, Germany and Austria pushing for change to the Vatican's approach to priest celibacy and women in the Church, to "radical feminist" nuns in the United States.