VATICAN CITY -- During his many years at the Congregation for the Doctrine of the Faith as well as during his pontificate, Pope Benedict XVI made incisive contributions to the search for Christian unity, although some of his teaching also was read as ecumenically insensitive.

While the late pope forged strong bonds of friendship and esteem with the leaders of the world' s Orthodox and Anglican Christians, his papacy also coincided with a difficult time in the search for full Christian unity.

In the face of new obstacles to ecumenism -- particularly regarding the ministry of women, attitudes toward homosexuality and differences on ethical issues -- Pope Benedict often emphasized the role of prayer in seeking Christian unity, as well as the need for divided Christians to work together to protect religious freedom and defend traditional Christian values.

From personal experience and theological study, his longest ecumenical engagement came in the area of Catholic-Lutheran relations.

Shortly after Pope Benedict resigned in 2013, the Rev. Nikolaus Schneider, then head of the Council of the Evangelical Church in Germany, told reporters at the Vatican how important the contributions of then-Cardinal Joseph Ratzinger were for the landmark 1999 Catholic-Lutheran theological agreement on justification, the dispute at the heart of the Protestant Reformation. Rev. Schneider also described as "historic" Pope Benedict' s decision in 2011 to visit the former Augustinian monastery where Luther lived until 1511.

The visit, though, left many German Lutherans disappointed. Somehow in the weeks before the visit, people started talking about the possibility that Pope Benedict either would lift the 500-year-old excommunication of Martin Luther or would make it much easier for a Lutheran married to a Catholic to receive Communion in the Catholic Church.

Neither happened. But Pope Benedict knew of the expectations and, in the monastery where Luther had lived, the pope said conjecture about him making an "ecumenical gift" demonstrated a "political misreading of faith and of ecumenism."

Progress in Christian unity is not like negotiating a treaty, he told his fellow Germans. Ecumenism will advance when Christians enter more deeply into their shared faith and profess it more openly in society, Pope Benedict said.

But Rev. Schneider also told reporters the German-born pope "offended" Protestants when, as head of the Congregation for the Doctrine of the Faith, in 2000 he insisted Protestant communities were not "churches in the proper sense" because they have not preserved apostolic succession among their bishops nor a traditional understanding of the mystery of the Eucharist.

Then-Cardinal Ratzinger repeatedly explained that the assertion in the document "Dominus Iesus" was simply a statement of Catholic belief, not a judgment of others. But particularly because the doctrinal congregation reviewed every joint ecumenical statement before publication, the statement cast a pall over the church' s dialogue with other Christian communities for several years.

For Catholics coming from the Anglican tradition, the ecumenical highlight of Pope Benedict' s pontificate was his decision in 2009 to establish personal ordinariates, jurisdictions similar to dioceses, which recognize their full communion with Rome while preserving some of their Anglican heritage.

But for many ecumenists, the move was not about Christian unity at all. Rather it was simply a pastoral provision for individuals and groups who, in conscience and after long prayer, sought full communion with Rome while not wanting to leave behind their spiritual, theological and liturgical heritage.

Even when ecumenical progress seemed slow, though, Pope Benedict continued to preach the importance of Christian unity and to recognize the duty of the pope to be its chief proponent.

After celebrating Mass April 20, 2005, in the Sistine Chapel with the cardinals who elected him pope the evening before, Pope Benedict, referring to himself, said he would assume as "his primary commitment that of working tirelessly toward the reconstitution of the full and visible unity of all Christ' s followers. This is his ambition, this is his compelling duty."