The Siege of Chartres was the part of Norman incursions. In 858 the Normans captured and burned Chartres. After that, in the time of relative peace, the town defenses were rebuilt and strengthened. It turned into a fortified, trapezoid-like city, going close to the river. When Rollo led the Danes in a siege, they were formidable enough to persuade Charles the Simple that they might become valuable allies. Richard, Duke of Burgundy split his forces into three corps.