On June 22, 1941, Germany launched what one today could call a preemptive strike on the Soviet Union in effect.
The argument made in Germany for war, beyond racial issues towards obviously the Jews and Slavs, and at least as important due to violent anti-Bolshevist sentiments in a lot of elite German quarters, was in no small measure that Russia was growing stronger at a pace that meant it would someday in the not too distant future surpass German power, which would be unsafe, and so getting the first punch in made sense: Barbarossa's rationale as preemptive strike.
It didn't work out that way of course, although when you look at present Russian demography, there is an argument that it did do permanent harm (one can see that it isn't unlikely that every Russian male after the war was desirable compared to what would have been the case absent the war, making for more unproductive, drunken, and generally not very fun Russian males, who then over time created a society that stopped reproducing itself, if that has improved lately).
As to the ambivalent effect of Barbarossa in the long run, an operation named for a German prince who drowned on Crusade in the late twelfth century, look at who matters still in international relations.
In Europe, when we talk of the EU and Euro surviving, we talk about Germans more than anyone else.
As to an ongoing German sphere internationally, in the Middle East, Israel's secure second strike nuclear platforms are on German-made Dolphin class submarines, because Germans are the Big Dog of Europe as to making things, submarines being on of the things they have been good at historically speaking. That's part of why Germany is part of the negotiations with Iran, since Barbarossa didn't totally fail, as to Germany ceasing to exist after its defeat.
At the same time in the Middle East, when we talk of Russian troop movements from the Black Sea to prop up Assad, or movements of Russian troops across the Caspian in the event of a strike on Iran, that is more like Nicholas I and the Crimean War in the 1850s than some totally new world altered by Barbarossa, as to wars started to permanently altering power relationships very often not having that effect, especially as to national cores like Germans and Russians, as opposed to Habsburgs and Romanovs ruling Poles.
So if D-Day was America's longest day, and Ivan and Jerry's longest day was the Summer Solstice of 1941, it does also reveal the truth so often of the French proverb: the more things change, the more they stay the same.