Pius XI files to be opened.

The Vatican said Friday that it was releasing from its secret archives all the files on the pontificate of Pope Pius XI, which spanned most of the period between World War I and World War II.

Researchers will be allowed to access the files beginning Sept. 18. They cover the period from Feb. 6, 1922, to Feb. 10, 1939.

In 2003, the Vatican began making available to scholars millions of documents from the years leading up to World War II, releasing them ahead of schedule at the request of Pope John Paul II.