Everyone knows how the Middle Ages ended. Gunpowder arrived, the armored horseman became a museum piece, castles fell, feudalism collapsed, and the modern world walked in through the breach. It is a wonderful story. Almost none of it survives contact with the evidence.

The finest plate armor ever made was produced after firearms were common, and the best armorers advertised their work by shooting it and leaving the dent. Heavy cavalry went on deciding battles for three hundred years after the first cannon appeared on a European field. The knight had already been beaten by Flemish weavers and Swiss farmers before powder mattered to anyone, and he had been drawing a salary since long before that. In Japan, guns arrived in 1543 and the samurai class survived until 1876—killed at last not by a bullet but by a conscription law.

This book conducts an inquest. It puts the usual suspects in the dock one at a time—the longbow, the pike, the arquebus, the siege bombard, the plague, the banker, the royal lawyer—and lets most of them go. What gunpowder actually destroyed was not the knight's body but the knight's castle, and only for about fifty years, until a new kind of wall restored the advantage of the defender at a price no private lord could ever pay again. That price is the hinge of the entire story. War did not become cheap and democratic. It became so expensive that only tax collectors could afford it.

The result is a history of how the map of Europe lost most of its colors, why the nobility survived the transition in excellent health, and why anyone watching a five-hundred-dollar drone destroy a ten-million-dollar tank today is repeating a very old mistake with great confidence.