In Episode 4 of A Red Line in the Sand, a companion podcast to the book of the same title, author David Andelman explores the red lines in the South China Sea - those built up by China, its neighbors like Vietnam and the Philippines, and Western powers like the US who fear losing naval passage.

In recent decades, China has increasingly become a world power, but it needs a world-class navy and sea-based control to truly claim its hold. And to do that, it needs indisputable power over the South China Sea.