Ancient civilizations in China, India, and Southeast Asia developed advanced cultures with centralized governments, occupational specializations, and religious beliefs. The Indus Valley and Shang civilizations exhibited organized urban planning, defensive structures, and social hierarchies. While the Indus civilization declined around 1500 BC possibly due to floods, climate change or invasion, the Shang fell in 1150 BC after being overthrown by a rival king, beginning China's Warring States period.