Joseph Ratzinger was not always considered a reactionary. Born in 1927 in Marktl am Inn, the first German pope for nearly 1,000 years comes from the country's traditionalist Catholic heartland, Bavaria.
His father was a police officer from a family of farmers whose career suffered because he refused to become a Nazi. The young Ratzinger served briefly and unenthusiastically with the Hitler Youth and later with a German army anti-aircraft unit guarding the BMW factory in Munich. He says he never fired a shot.
Ratzinger has defended himself from criticism of his war record by claiming - not strictly truthfully - that he could not have avoided military service in the circumstances. Others did and maybe he could have used his training in a seminary to dodge the call-up.
But there is no doubt that his heart was not in his military service and he deserted in April 1945, briefly becoming a prisoner of war.
Ordained with his older brother, Georg, in 1951, Ratzinger was a liberal theological adviser at the Second Vatican Council in Rome but became a conservative after the 1968 student movement prompted him to defend the faith against secularism.
In his autobiography, he wrote how he realised he was increasingly out of step with his fellow Germans as early as the 1960s.
"I found the mood in the church and among theologians to be agitated," he recalled. "More and more there was the impression that nothing stood fast in the church, that everything was up for revision."
He has written a number of books and within hours of his election as pope yesterday, several leapt up the Amazon bestseller list, including Salt of the Earth, The Ratzinger Report, Introduction to Christianity, and his memoirs, Milestones, which cover his life until 1977.
It was in 1977 he became archbishop of Munich and a cardinal. He was one of only two cardinals in the conclave that ended yesterday to have been elevated by John Paul's predecessor but one, Paul VI.
In 1981, Pope John Paul called him to Rome to take over the Congregation for the Doctrine of the Faith. It is the department that was once known as the Holy Inquisition.
Ratzinger's defence of conservative orthodoxy has been part of his job. But it has not made him popular, especially in more progressive corners of the faith.
An opinion poll in the German newspaper Der Spiegel found opponents of his election as pope outnumbering supporters by 36% to 29%.
It was an open secret before the conclave that all but two of the German bishops were opposed to his candidacy.
In western Europe and North America, in particular, there is an acute perception that the church is losing ground and needs to reinvigorate its flock with a less uncompromising hostility to the outside world.
In Latin America, he disciplined the advocates of "liberation theology" and cracked down on Asian priests who saw non-Christian religions as part of God's plan for humanity.
Before the death of Pope John Paul, his theological watchdog spoke passionately of the need to clean up the "filth" in the church, an allusion to successive child abuse scandals involving clerics. His remark held out hope that he would tackle vigorously one of the church's most pressing problems.
However, he has himself been accused by campaigners of shielding a prominent alleged paedophile.
The softly spoken Bavarian, who is an accomplished pianist with a fondness for Mozart, turned 78 last Saturday, but is in apparently excellent health.
Three years ago, he became dean of the College of Cardinals, a position which made him the key figure in the interregnum between popes and enabled him to exert immense influence on his fellow cardinals as they prepared to choose the next pontiff.
At Pope John Paul's funeral, he impressed his listeners by deftly balancing solemnity and populism in his homily. He drew roars from the crowd when he pointed to the window from which the late pope had delivered his blessings, saying: "We can be sure our beloved Pope is now at the window of the house of his Father and he sees us and he blesses us."
Days later, he seized the initiative again at the mass immediately before the start of the conclave when he inveighed against the moral relativism of today's society. In what was seen by Vatican insiders as a blatant campaign speech, he warned the church to withstand the "tides of trends and latest novelties".
Clearly, his fellow cardinals were listening hard.
But when looking at his life so far, it is hard to know which is more memorable: the things that have been said about Ratzinger or what he has himself said.
Five years ago, a former colleague in the theological faculty of Tübingen University, Hans Küng, whom he banned from teaching on the church's behalf in 1979, described a document published by Cardinal Ratzinger's department in the Vatican as "a hotch-potch of medieval backwardness and folie de grandeur".
He was referring to the document Dominus Jesus issued by the Congregation for the Doctrine of the Faith in Rome, which, in highly unecumenical language, described other Christian faiths and world religions as "deficient or not quite real churches". When the Lutherans complained, the future Benedict XVI dismissed their objections as "absurd".
Another liberal Catholic and former priest, the late Peter Hebblethwaite, called him "the big, bad wolf of the new Inquisition ... For some, the thought [of his becoming pope] is just too terrible to contemplate. To have him as pope would be inconceivably divisive, runs the common wisdom."
It is not just people who do not believe in Roman Catholicism who attract the new pope's ire. Four years ago, he wrote that rock music was "the expression of elemental passions which, in the big musical festivals, have taken on a cultural character, that is to say, [the character] of a counter-cult, opposed to Christian worship".
Only this week, he declared that "having a clear faith based on the creed of the church is often labelled today as fundamentalism. Relativism, which is letting oneself be tossed and swept along by every wind of teaching, looks like the only attitude acceptable to today's standards."
Small wonder that the 78-year-old German has won nicknames such as God's Rottweiler and the Panzer Cardinal. Even Corriere della Sera, the voice of the Italian moderate right, which is normally deeply respectful of the church hierarchy, recently labelled him "Cardinal No".
For the past 24 years, he has headed the Vatican "ministry" responsible for defending and enforcing Catholic orthodoxy, particularly in the world's theological faculties.
Ratzinger once denied being "the Grand Inquisitor".
However, under his guidance, the Congregation for the Doctrine of the Faith has issued a stream of hardline instructions and rebukes.
The hand of the new pope has been seen in most of the more reactionary proclamations made by the Vatican in the final years of John Paul II's papacy, as his health waned.
They sometimes took away the breath of the more progressive elements in the church: from denouncing homosexuality as intrinsically evil, to suggesting that parishes should limit the use of female altar servers and choristers.