Obama in Berlin for landmark assembly

Former US President Barack Obama and German Chancellor Angela Merkel spoke in front of tens of thousands of people before the Brandenburg Gate in Berlin on Thursday to discuss God, faith and the state of the world.

Speaking on a panel on the first day of Germany's Protestant Church Assembly, Obama praised Merkel's "outstanding work" and described her as one of his "favorite partners" during his eight years in office. He lauded Merkel's handling of the refugee crisis, while at the same time reflected that he "didn't always have the tools" to end the war in Syria. 

"Despite our best efforts, there is a vicious war," Obama said.

The former US president warned of succumbing to nationalism and a closed world - an apparent reference to US President Donald Trump. 

- Reports: Obama warned Trump about Flynn's Russian ties

- Obama makes first public speech since leaving office

"In this new world we live in, we can’t isolate ourselves, we can’t hide behind a wall," he said before the gate that once separated East and West Berlin. 

Obama has made few appearances since leaving office. He said he spent time with his family, working on his foundation for youth and catching up on lost sleep. 

Obama is the most famous guest among the approximately 140,000 expected participants at the four-day "Kirchentag."  

It is a star-studded occasion: 2,500 events, 30,000 contributors and guests from all over the world celebrating the 500th anniversary of the Reformation and the Protestant culture of debate.

More than 100,000 worshippers attended three open-air services on Wednesday evening in central Berlin to mark the start of the Protestant gathering. 

Those attending include Archbishop of Cape Town Thabo Makgoba, Grand Imam of Cairo's Al-Azhar Mosque Sheik Ahmed el-Tayyib, philanthropist Melinda Gates, German singer and songwriter Max Giesinger, German climate change researcher Ottmar Edenhofer, UN envoy Staffan de Mistura and Israeli author Amos Oz.

A new movement

The German Protestant Church Assembly, or "Kirchentag," which has been held every two years since 1949, is an international and yet typically German event at the same time. It was founded by the East Prussian politician Reinold von Thadden, a member of the Confessing Church, which opposed the Nazi regime. Von Thadden was active in the resistance during the Nazi era and later acted as president of Kirchentag until 1964.

"Apart from the Confessing Church branch, the Protestant Church did not play a laudable role in National Socialism," says Protestant Church Assembly spokesperson Sirkka Jendis. "That is why dedicated lay people said, 'We need to create a forum to help ensure that something like that cannot happen again.'"

From the "Protestant Week" in Hanover in 1949 emerged a Protestant lay movement that deliberately set itself apart from the official church and held regular congresses. "The broad scope and public relevance is unique," says Jendis. In view of the numerous panels on subjects including the flight of refugees, migration, war, tolerance and integration, she says it is clear to her that, "this Church Assembly may become political."

Controversial guests

Current Protestant government leaders in Germany will participate in this year's congress: German Finance Minister Wolfgang Schäuble will discuss what is holding Europe together, the Social Democratic Party's (SPD) chancellor candidate Martin Schulz will talk about credibility and German President Frank-Walter Steinmeier will take part in the holiday church service in Wittenberg.

German Interior Minister Thomas de Maiziere's whirlwind participation will see him make seven Kirchentag appearances, including one together with Al-Azhar's Sheik Ahmed el-Tayyib. "I think it is great that he is coming to join the discussion," de Maiziere told the German weekly newspaper Die Zeit. "Controversial guests like him are a gain for the Church Assembly."

But Protestant debate culture also has its limits. There was great opposition to the invitation of 43-year-old Anette Schultner, the national spokesperson of "Christians in the AfD," a Christian organization of the Alternative for Germany (AfD), a right-wing populist political party. She wants to explain to visitors why their faith and their membership in the AfD are compatible with each other.