Brad DeLong says he's not sure "if this is a very good or very bad end-of-lecture sentence":
Next time, I'll talk about Adolf Hitler, whose big problem--besides being a bloodthirsty persuasive paranoid genocidal psychopath, that is--is that he pays to much attention to (a) Malthus, (b) social darwinists, and (c) cowboy novels.
Seems good to me. The answer, I think, is (a). Hitler suffered from, among other things, a Malthus-esque belief that "the power of the earth to produce subsistence for man" for sharply limited and that the acquisition of land -- lebensraum -- was crucial to national prosperity. Thus, he decided to invest a massive proportion of the German economy in a fruitless effort to greatly expand Germany's land area. But instead of a larger land area, Hitler's policies wound up making Germany smaller. And in destroying a huge proportion of Germany's capital infrastructure. And in subjecting a substantial portion of Germany to decades of Communist rule. And at the end of the process, Germany does, indeed, have a higher population density than Italy or France or Spain.
And yet: Germany is a really rich country in the scheme of things, especially the Western part. Because Hitler was wrong. German prosperity doesn't depend on acquiring more land and never did.