Einstein's letter urging Roosevelt to build world's first atomic bomb to be auctioned

A letter from Albert Einstein, which encouraged the US to develop the world's first nuclear bombs, is to go up for auction, reports the BBC.
Written to President Franklin D. Roosevelt on 2 August 1939—just weeks before the Second World War was declared—the note warns that Nazi Germany might be able to create such weapons, and suggests the US begins its own atomic program.
Three years later, America began the Manhattan Project, which led to the first ever use of atomic weapons, against Japan, in 1945.
But Einstein is reported to have later regretted the letter due to its role in making America the only country—at the time—to make nuclear weapons.
The letter is being sold as part of an auction of artifacts belonging to Microsoft co-founder Paul Allen, who died in 2018 at the age 65.
His personal collection is go on sale at Christie's, in New York, in September.
There will be a range of items reflecting his interest in—and influence on—computing, but the Einstein letter is expected to be the centerpiece.
It has been given an estimated value of between $4 million and $6 million.