The letter from the pope to the U.S. president about the war was diplomatically florid, but clear in its message.

“Our contemporaries follow with their heartfelt prayers, and posterity will hold in honored memory, all those who — undeterred by immense difficulties — dedicate themselves to the sacred task of staunching the flow of youthful blood upon the fields of battle, and to the comforting of civilian victims despoiled and afflicted by the cruel conditions of our day,” it said. “Blessed, indeed, are the peacemakers.”

The year was 1940. Franklin D. Roosevelt was president, and the war about which Pope Pius XII agonized was World War II.

A series of memos and letters between the two leaders and their surrogates touched on efforts to avoid, then end the war; concerns for refugees and the fate of Christians in Russia; and worries about Allied bombing killing civilians and destroying important historic and religious sites in Rome.

As President George W. Bush prepares to welcome Pope Benedict XVI to the White House April 16, one topic widely expected to surface during their private meeting and during the pope’s address to the United Nations April 18 is the five-year-old U.S.-led Iraq War and how to end it. As recently as March 17, Pope Benedict stepped up appeals for an end to the “bloodbath and hatred” tearing apart Iraq.

Pope Benedict pleaded for “reconciliation, forgiveness, justice and respect for the civil coexistence among tribes, ethnicities and religious groups” to be the path to achieve peace. Pope John Paul II had been a fierce critic of the invasion of Iraq and made a point of reminding Bush of the Vatican’s unequivocal opposition to the Iraq War during the president’s 2004 visit to Rome.

The Roosevelt collection illustrates that diplomatic relations between the Vatican and the White House have historically involved unified strategies as well as differences of opinion. At the time of the pope’s March 1940 letter, Germany had invaded Poland and Czechoslovakia and tensions across Europe were high.

Four months earlier, Roosevelt had angered supporters of strict separation of church and state when he reversed a policy of more than 70 years by appointing Myron Taylor as a formal diplomatic representative to the Vatican. The United States has had some kind of diplomatic link to the Vatican most of the time since 1784, though relations were informal for decades after a political misunderstanding in 1867.

After the war, President Harry S. Truman attempted to name Gen. Mark Clark full ambassador to the Vatican, but withdrew the nomination in the face of public controversy.

For nearly 20 years the post of personal representative to the Vatican remained vacant. Presidents Richard Nixon and Jimmy Carter named personal envoys, but it wasn’t until 1984 under President Ronald Reagan that the United States established formal diplomatic relations with the Vatican.

The archive of Roosevelt’s interactions with the Vatican consists of correspondence between the president and the pope and Taylor’s telegrams and memos recounting his meetings and discussions with Pope Pius and Vatican Secretary of State Cardinal Luigi Maglione.

A memo from September 1942 touches on some topics that sound remarkably contemporary. In it, Taylor recounted a meeting with Cardinal Maglione that dealt with how a post-war Europe would be constituted. “It is the opinion in Vatican circles, expressed both by the pope and the cardinal, that great disorder will prevail, and both have some doubt as to the ability of the United Nations or other influences to suppress it,” Taylor wrote.

Taylor said Cardinal Maglione also voiced the Vatican’s concern that it was difficult to envision the political, territorial and economic makeup of Europe after the war “and that, with a great variety of languages, political traditions and the hatreds engendered by war, as well as those which have for long previous periods existed, make very difficult the organization of such states in a cooperative way.”

Substitute “Iraq” for “Europe” and the excerpts might have an echo in the speeches and private meetings in coming days.