Oh it was longer than that. Just clearing the rubble took a decade. It was the 70's before we started seeing european tourists in any numbers. Because they were all dead or displaced. Like 20 million plus 30 million displaced, just in Europe, up to 40 million Russians. Two ladies from Denmark owned a restaruant where I grew up. I later read a story of their exploits in the Resistance. They hunted Nazi quizlings and killed a bunch.
World population was 2.3 billion in 1945, extrapolated out a similar war now might take 3X as many, 200-300 million worldwide. But with how civilians are targets now a billion or more is conceivable.