When a complex system starts to decay, the first signs are usually subtle. In the third century, after the Roman empire had reached its geographic maximum, literacy began to decline across Roman society. Education levels fell not only among soldiers, but among officers, aristocrats, and even emperors. The Roman army still looked formidable for years afterward. It had good equipment and could march well. Yet it was no longer as advanced relative to Rome’s enemies as it had once been. It fought as hard as ever, but less effectively.