On this Day - 1939, the #Nazi-#Soviet Pact was announced in Moscow. As well as a 10-year Non-Aggression Pact, Stalin and Hitler agreed to divide central Europe between them. Here, Stalin toasts the pact with Hitler's photographer, Heinrich Hoffmann.

The Nazi-Soviet Pact gave #Hitler the green light for his plans to invade Poland: a week after its signature, German forces invaded their eastern neighbour. Poland's allies - Britain and France - responded by declaring war on Germany on 3 September. #WW2 in Europe had begun.

Two weeks later, on 17 September, #Stalin's Red Army also invaded #Poland, to claim the spoils promised by the Pact with Hitler. The two invading forces met at Brest-Litovsk, where a joint Red Army/Wehrmacht parade was held, with German and Soviet troops happily fraternising.

#Poland would disappear from the map - divided down the middle between the Germans and the Soviets - subjected to yet another Partition. Here is the map used for the deliberations in Moscow. #Stalin signed it in blue crayon, Ribbentrop in red.

Peculiarly, the #Nazi-#Soviet Pact remains a largely overlooked episode. If you want to know more about it, have a look at my 2014 book "The Devils' Alliance", which is also available in Polish, Czech, Danish, Estonian, Swedish, Dutch, Lithuanian and Slovak.