Neither Stalin nor Roosevelt could have had any idea early in 1941 that they would become distant pen pals by the year’s end. Eventually they wrote more than three hundred messages between them, the fruit of a collaboration forged from the German attack on the Soviet Union in June 1941 and the Japanese attack on Pearl Harbor almost six months later which made the two leaders into involuntary allies.

Little of this correspondence is unknown. Published collections of documents from the 1950s have included many of the letters, if incomplete or doctored in some way. They have long been in the public domain in the sense that researchers could go to the Franklin D Roosevelt Library in Hyde Park,