Bangladesh, Sept. 21 -- The latest collision near Xianbin Jiao, known internationally as Sabina or Escoda Shoal, has once again exposed how quickly the South China Sea can turn from a maritime dispute into a geopolitical crisis. On September 18, China and the Philippines issued sharply conflicting accounts of what happened. Beijing said Philippine vessel 3015 ignored repeated warnings, altered course and accelerated across the bow of a China Coast Guard ship, causing the collision. Manila offered the opposite account, accusing the Chinese vessel of ramming the Philippine government ship during a patrol mission.

The disagreement over who was responsible matters, but the larger question is perhaps even more important: why do these encount...