Nazi Germany and its allies launch a massive invasion of the Soviet Union, opening the Eastern Front, the largest theatre of the Second World War.
Nazi Germany and its collaborators systematically murder some six million European Jews, along with millions of other victims.
German and Finnish forces besiege Leningrad for nearly 900 days; around a million civilians die, mostly from starvation.
The Royal Air Force repels a large-scale air campaign by the Luftwaffe, forcing Hitler to postpone his planned invasion of Britain.
Senior Nazi officials meet at Wannsee near Berlin to coordinate the "Final Solution" to murder Europe's Jews.
The Red Army encircles and forces the surrender of the German Sixth Army, a decisive turning point on the Eastern Front.
Soviet and Mongolian forces under Georgy Zhukov defeat the Japanese on the Mongolian–Manchurian border.