An increasingly belligerent Vladimir Putin is finding a new friend in a man of peace: Pope Francis.

The Vatican’s secretary of state, Cardinal Pietro Parolin, is scheduled to fly to Moscow on August 20 to meet the Russian president and Patriarch Kirill, the head of the Russian Orthodox Church.

The four-day visit — the first of its kind since the Russian annexation of Crimea in 2014 — is another step in a deepening relationship that began in September 2013, when Francis wrote an open letter to Putin, who was chairing the G20, to express his opposition to a U.S. military intervention in Syria.

In that letter, “the Pope asked Putin to pray for him, and it seems this line touched Putin,” said Andrea Riccardi, the founder of the Rome-based Sant'Egidio community, a humanitarian organization that sometimes serves as an unofficial arm of Vatican diplomacy.

The request — unusual for a diplomatic letter — was a recognition of the Christian identity Putin has assiduously cultivated. Putin no doubt also appreciated the Pope's message given that the Kremlin was one of the more vocal critics of U.S. military action in Syria.

“Like Trump, Francis faces criticism from his base over his Russia policy" — John L. Allen, author on the Vatican

A few months later, in November, Putin went to Rome to meet Francis for the first time (he had already met his predecessors, John Paul II and Benedict). The Russian president showed up about 50 minutes late but this didn't stop the pope from welcoming him again in June 2015 (when Putin was more than an hour late). Francis greeted Putin in German, and the meeting lasted 50 minutes, far longer than Francis’ meeting with U.S. President Donald Trump, which went on for 29 minutes.

For Putin, a visible relationship with the Vatican is an opportunity to highlight Russia's effort to portray itself as a bulwark of morality and traditional values in contrast to an increasingly secularized Europe.

Like hosting the Winter Olympics in 2014 or football’s World Cup next year, the friendly ties with the Vatican are a way of showing the Kremlin is not isolated, even as it remains under sanctions. An open line to the Vatican also helps the Kremlin maintain its relationship with Italy, still one of Russia’s biggest friends in the European Union.

“The Holy See can't do much on the sanctions” the U.S. and the EU have slapped on Moscow over its invasion of Ukraine, said Stefano Caprio, who spent over 10 years in Russia in the 1990s as one of the few Catholic priests in the country, and now teaches Russian culture at the Pontifical Oriental Institute in Rome.

But photo ops with the pope buttress the Russian president’s attempts to present Russia as a stronghold of Christianity working to save a corrupted Western civilization from globalization without values — an effort that has sparked a debate in the Catholic world about whether Russia can indeed provide such a solution.

Rome, Constantinople, Moscow

Russian conservatives have even resurrected czarist rhetoric of Moscow as a "third Rome," a center for imperial Christianity (the second being Constantinople).

For the Roman Catholic Church, tighter ties with Moscow are an opportunity to reestablish a stronger presence after a century marked by the rise and fall of communism and enforced atheism. Officially, freedom of religion is enshrined in the Russian constitution, but that hasn't stopped the government from making things difficult for religions other than the Orthodox Church. At the start of the new century, tensions rose and a few priests and bishops were kicked out of the country after being accused of proselytism by the Orthodox Church. Full diplomatic relations between Moscow and the Vatican were only restored in 2009.

While some media pundits speculate that Vatican Secretary of State Parolin’s trip could pave the way for the first ever visit of a Catholic pope to Moscow, most analysts believe Orthodox opposition makes that eventuality remote.

Such a move, however, would be in line with what Iacopo Scaramuzzi, an expert at the website Vatican Insider, says is the pope’s desire “to unify Christians.”

In February 2016, a meeting between Francis and Russia's Patriarch Kirill at Havana airport in Cuba marked the first meeting between a Moscow patriarch and a pope since the Eastern Orthodox church broke away from Rome in 1054. The meeting took almost 20 years of preparation and resulted in a joint declaration.

“Now things are easier,” said the Russian cleric.

“It's clearer that this is God's will,” replied the Argentine pope.

Christians in the Middle East have also been broadly supportive of Russia’s backing for President Bashar Assad in Syria, which is expected to be high on the agenda during Parolin’s meeting with Putin.

“For Syrian Christians, the Assad regime was a shield against fundamentalism,” said Riccardi. “The Holy See doesn't have the same line, but it's very sensitive to the way other Christians see the situation.”

Middle Eastern Christians tend to be close, in belief and history, to the Russian Orthodox Church, said Matteo Matzuzzi, a Vatican analyst at the Rome newspaper Il Foglio. “So, at a time when Christians are threatened in that region, the Holy See may appreciate a Russian presence that tries to defend them."

'Fratricidal war'

One area of tension could be Russia’s aggression in Ukraine, on which Francis has come under fire for having taken a soft stance.

“Like Trump, Francis faces criticism from his base over his Russia policy,” wrote John L. Allen, author of several books on the Vatican and Catholic affairs. “Many Catholics charge him and the Vatican with excessive 'ecumenical correctness,' insisting that he should be more outspoken on Ukraine.”

“I do not think that you can say that the country, even in the moments of greatest difficulty, ever left the international scene" — Cardinal Pietro Parolin on Russia

Francis has called the conflict “fratricidal war,” laying blame on both sides — angering Greek Catholics who live in Ukraine. Their Major Archbishop, Sviatoslav Shevchuk, was quoted as saying that "many contacted me and said that they feel betrayed by the Vatican."

In a recent interview in the Catholic magazine Il Regno, Secretary of State Parolin recognized Russia's role on the world stage.

“I do not think that you can say that the country, even in the moments of greatest difficulty, ever left the international scene,” he said. But he also made clear that “the effort to understand each other does not mean the yielding of one to the position of the other.”

David M. Herszenhorn contributed reporting.