How the “nine-dash line” fuels tensions in the South China Sea

CHART THE course of Chinese coastguard ships in the South China Sea and a pattern emerges. The boats’ patrols often follow a U-shaped route that stretches over 700 nautical miles from China’s coastline, encircling most of a sea that plays an outsize role in global trade and security. This path is the “nine-dash line”. China claims everything inside it as its own, ignoring protests from neighbouring countries. Last year its coastguard spent longer patrolling key reefs along the line than ever before. China’s assertiveness in enforcing this claim is perhaps the biggest obstacle to calming tensions in the South China Sea. How did this line become so important?