With the north and east pacified and a large military force under his control, King Zhao turned his attention to the Yangtze basin. This region of great mineral wealth was under the control of the confederation of Chu, with whom the Zhou kingdom had been on good terms for almost two centuries. Under King Zhao, the relationship between Zhou and Chu deteriorated, however, as Chu continued its aggressive expansion and Zhou's demand for gold, copper and tin grew. As hostilities grew, border clashes ensued that eventually escalated into open war. No longer tolerating Chu's perceived defiance, Zhao invaded the Chu confederation in 961 BC. He initially conquered the region to the north of the Yangtze, and then defeated and subdued the 26 states of the Han River valley, including Chu. Most likely unable to permanently occupy the latter region, Zhao eventually retreated with much loot.