Stalin kept demanding the second front and knew we were letting the Sovs bleed Hitler and themselves. But, he had no choice. We were not going to open that front until we had an army of sufficient size properly trained and equipped. As it should have been.
I ran across a YouTube series called The Great War. Each episode is about 15 minutes and covers one week. I'm into 1917. The losses were staggering. The stupidity of the leaders was staggering. And the Austrians stood out as idiots by those low standards. But I can't stop watching it! No wonder WWI permanently changed the way Europeans viewed and fought wars. It explains why they tried appeasing Hitler for way too long.
The British could not fight WWII the same way they fought WWI - they simply did not have that kind of manpower to throw away.
When the Americans saw how the Europeans were fighting the war they knew there had to be a better way. The Army adopted fire and maneuver as its basic offensive strategy, discouraging frontal assaults. Between the wars the artillery was reorganized and a new fire control system was adopted. By WWII, US artillery was the deadliest and most accurate in the world - and we deployed plenty of it. Still, in the Army only a few visionaries like Patton anticipated the impact the tank would have and the possibilities for mobile warfare.
Stalin kept demanding the second front and knew we were letting the Sovs bleed Hitler and themselves.
The US wanted to go in, the British didn't. Britain was the staging area, so, we didn't go. Again, the British had bled themselves out in WWI, even though they won't ever quite admit it to this day -- usually the closest they'll get is to claim that the Germans lost because they were running out of men. Had the Germans suffered the KIAs and other casualties at the same rate as the British, they'd never been able to fight WWII.
Between WWI, the Russian civil war (often euphemistically and inaccurately referred to as the Russian Revolution), the purges between the wars, and WWII, the Russian Empire/USSR lost over 38 million (1.5 million WWI, 20-40 million in the civil war and subsequent purges, 16 million WWII). Of course, the Reds are responsible for most of those, plus another 20 million or more in China, millions more in their conflicts around the world, not to mention the fact that they trained up the first generation of 20th c jihadists.