During the long nights of the second Ottoman siege of Vienna in 1683, the Viennese were unnerved by the nightly scratching and chipping of the Turkish sappers, seemingly just under their floorboards, as they worked to plant mines to force a breach in the walls. The siege failed and the Grand Vizier Kara Mustafa, commander of the Ottoman forces, paid the price for his failure: he was strangled by janissaries with a bowstring. But something akin to that spooky and ominous scratching seems to have rattled the minds of some of the greatest European political thinkers, from the fall of Constantinople in 1453 under the forces of Sultan Mehmed II to the mid-18th century. The Ottomans who preoccupied these thinkers – ranging from Machiavelli to Montesquieu – may have been as invisible as the Turkish sappers, but they loomed large in theories of state. And yet, as Noel Malcolm shows in this brilliant and densely detailed study, the Turks were as useful to European thinkers as they were menacing.