A suburban Boston museum with a huge trove of World War II-era items has acquired two key documents, including one from the Germans demanding the U.S. surrender.

The Natick-based Museum of World War II says the latest additions "epitomize the American spirit at the end of the war."

The museum says it acquired the English version of a German letter demanding the U.S. surrender at Bastogne, Belgium, in 1944.

That demand prompted U.S. Gen. Anthony McAuliffe's legendary retort: "NUTS!"

McAuliffe and the 101st Airborne Division were able to hold Bastogne during the Battle of the Bulge, considered one of the U.S. military's greatest triumphs.

The museum says it's also acquired an original and previously unknown mimeographed period copy of the Potsdam Proclamation, which had called for Japan's unconditional surrender.