‘It’s been our misfortune to have the wrong religion,” Hitler complained to his pet architect Albert Speer. “Why did it have to be Christianity, with its meekness and flabbiness?” Islam was a Männerreligion—a “religion of men”—and hygienic too. The “soldiers of Islam” received a warrior’s heaven, “a real earthly paradise” with “houris” and “wine flowing.” This, Hitler argued, was much more suited to the “Germanic temperament” than the “Jewish filth and priestly twaddle” of Christianity.

For decades, historians have seen Hitler’s Beer Hall Putsch of 1923 as emulating Mussolini’s 1922 March on Rome. Not so, says Stefan Ihrig in “Atatürk in the Nazi Imagination.” Hitler also had Turkey in mind—and not just the 1908 march of the Young Turks on Constantinople, which brought down a government. After 1917, the bankrupt, defeated and cosmopolitan Ottoman Empire contracted into a vigorous “Turanic” nation-state. In the early 1920s, the new Turkey was the first “revisionist” power to opt out of the postwar system, retaking lost lands on the Syrian coast and control over the Strait of the Dardanelles. Hitler, Mr. Ihrig writes, saw Turkey as the model of a “prosperous and völkisch modern state.”

As David Motadel writes in “Islam and Nazi Germany’s War,” Muslims fought on both sides in World War II. But only Nazis and Islamists had a political-spiritual romance. Both groups hated Jews, Bolsheviks and liberal democracy. Both sought what Michel Foucault, praising the Iranian Revolution in 1979, would later call the spiritual-political “transfiguration of the world” by “combat.”

The effects of Germany’s ideological seeding of Muslim societies in the 1930s and ’40s are only now becoming apparent.

Impeccably researched and clearly written, Messrs. Motadel and Ihrig’s books will transform our understanding of the Nazi policies that were, Mr. Motadel writes, some “of the most vigorous attempts to politicize and instrumentalize Islam in modern history.”