The launching of Operation Barbarossa 80 years ago to the day

Why did the Nazi’s wait until the end of June to invade the Soviet Union? Obviously Hitler assumed that taking the Soviet Union was going to be a cinch. He underestimated Russian nationalism but also socialism. The upshot was not Brest Litovsk (which finalized Russia’s defeat in WW I) but the taking of Berlin by the Red Army (with casualties that towered those of Normandy). Those who claim that socialism has proven to be a total failure should compare 1917 with 1945.