Andrew’s successor, Béla IV (1235–70), began his reign with a series of measures designed to reestablish royal authority, but his work was soon interrupted by the frightful disaster of the Mongol invasion. In the spring of 1241 the Mongols quickly overran the country and, by the time they left it a year later, inflicted ghastly devastation. Only a few fortified places and the impenetrable swamps and forests escaped their ravages. The country lost about half its population, the incidence ranging from 60 percent in the Alföld (100 percent in parts of it) to 20 percent in Transdanubia; only parts of ...(100 of 37110 words)