Hours after Pope Benedict XVI sent a letter to Iran’s spiritual leader Ayatollah Khamenei last month, appealing for the release of 15 British Navy sailors taken captive in Iran, all of them were set free.

On March 23, Iran’s Revolutionary Guard captured the sailors for allegedly trespassing in Iranian waters. Tensions in the region were high, and numerous attempts to free the hostages through diplomatic channels failed.

The Pope then wrote to Khamenei asking for release of the sailors as a good will gesture before Easter. Shortly afterwards on April 4, Iranian President Ahmadinejad announced he was releasing the sailors as an Easter “gift” for Britain.

Some argue the sailors were freed primarily because the United States released an Iranian in custody in Iraq on suspicion of helping Iraqi insurgents. Other observers, however, believe the Pope’s letter was crucial, citing similar language used by the letter and Ahmadinejad.

Speaking to the Register April 24, Mohammed Javad Faridzadeh, Iran’s ambassador to the Holy See, said his embassy “received the Pope’s letter with great happiness.”

“We immediately sent it to Iran as we know the spiritual importance the Vatican has throughout the world,” he said. “The moment when the Pope wrote that letter, it became a matter of importance.”

Francis Campbell, Britain’s ambassador to the Holy See, said that he was sure the letter, along with other diplomatic efforts, was influential in securing the sailors’ release. However, he would not comment on whether the letter was Britain’s initiative or whether the letter directly triggered the crisis’ resolution.

Said Campbell, “We have to keep certain channels of communications and conclusions confidential.”

But if the letter was pivotal in resolving a delicate and dangerous situation — as it appears to have been — why doesn’t the Holy See intervene directly in more international disputes?

The main reason is the necessity for both conflicted parties to accept the Vatican as a formal mediator. The last time that occurred was the “Beagle Channel” conflict in 1978, when Argentina and Chile almost went to war over a cluster of small islands at the southern tip of South America.

As the crisis worsened, Pope John Paul II sent an envoy, Cardinal Antonio Samoré, who began a process of Vatican mediation lasting six years.

“It was successful because of the diplomatic ability of the Holy See’s representatives,” said Franciscan Father David Maria Jaeger, a canon lawyer and expert in Vatican diplomacy. “There was also a readiness to accept whatever the Holy See was to decide.”

One reason the Holy See has not been able to intervene similarly in the Palestinian-Israeli conflict is because Israel has consistently declined mediation, preferring direct negotiation with opposing states. But the Pope and the Vatican regularly make ad hoc appeals for peace and dispatch envoys in the Middle East and other troubled regions.

For example, Pope John Paul II sent Cardinals Pio Laghi and Roger Etchegaray respectively to Washington and Baghdad in early 2003 to try to avert the Iraq war. More recently, say Vatican sources, Benedict considered sending an envoy to Lebanon when it threatened to collapse again into civil war.

And on April 24, Benedict held an audience with Mahmoud Abbas, president of the Palestinian Authority.

“In the course of the cordial discussions, attention turned to the situation in the Middle East,” the Holy See Press Office said in a statement. “Particular appreciation was expressed for the commitment — thanks also to the help of the international community — to relaunch the peace process between Israelis and Palestinians.”

Ambassador Campbell said the Vatican’s diplomatic strengths derive from its capacity to unite both the local and the global. It is not just a state of 109 acres, he said, but the headquarters of an institution with a network of 1.1 billion adherents and a structure that has a “cascading link down to a grassroots structure on a global scale that virtually no other country has.”

Iran’s Faridzadeh said that because the Vatican is both a political and religious state, it can better understand an Islamic state like Iran.

He also sees the Vatican as a key gateway. “As an important pillar of the West, Catholicism is in a relevant position to facilitate communications between the West and Iran,” he said. “This makes the Vatican the best intermediary.”

Some observers have suggested a Vatican office dedicated to mediating international disputes could be worthwhile.

“If asked, I don’t see why not,” Cardinal Renato Martino, president of the Pontifical Council for Justice and Peace, said about the creation of such an office.

Noted Cardinal Martino, “The Holy See, the Pope, always have been available for mediation, starting in the 16th century and through the centuries.”

Edward Pentin writes from Rome.