Why is China willing to stake everything on the South China Sea?

The real reason China is so determined to control the South China Sea goes far beyond access to natural resources.
This region forms a key part of China's national security strategy known as the First Island Chain, a geographic buffer zone that Beijing views as critical to preventing foreign military forces—especially the United States—from projecting power near its coast.
By dominating the South China Sea, China aims to limit U.S. influence in the Asia-Pacific region and secure strategic control over key maritime routes essential to both trade and military operations.