In 376, the Ostrogoths, fleeing from the Huns, received permission from Emperor Valens (r. 364–378) to settle in the Roman province of Thracia in the Balkans. The settlement did not go smoothly, and when Roman officials mishandled the situation, the Ostrogoths began to raid and plunder.[D] Valens, attempting to put down the disorder, was killed fighting the Ostrogoths at the Battle of Adrianople on 9 August 378. As well as the threat from such tribal confederacies from the north, internal divisions within the empire, especially within the Christian Church, caused problems. In 400, the Visigoths invaded the Western Roman Empire and, although briefly forced back from Italy, in 410 sacked the city of Rome. In 406 the Alans, Vandals, and Suevi crossed into Gaul; over the next three years they spread across Gaul and in 409 crossed the Pyrenees Mountains into modern-day Spain. The Migration Period began, where various people, initially largely Germanic peoples, moved across Europe. The Franks, Alemanni, and the Burgundians all ended up in northern Gaul while the Angles, Saxons, and Jutes settled in Britain. In the 430s the Huns began invading the empire; their king Attila (r. 434–453) led invasions into the Balkans in 442 and 447, Gaul in 451, and Italy in 452. The Hunnic threat remained until Attila's death in 453, when the Hunnic confederation he led fell apart. These invasions by the tribes completely changed the political and demographic nature of what had been the Western Roman Empire.