SINGAPORE — Is China becoming more assertive in enforcing its claims to control as much as 80 percent of the South China Sea, a claim that includes sovereignty over dozens of islands disputed with several Southeast Asian states?

Recent developments certainly point in this direction. Japan, the United States, India and Australia — all powers with a strong stake in regional stability — are watching the situation closely.

In an apparent demonstration of its growing maritime enforcement capabilities, the Chinese navy last month ended a long-range deployment into the South China Sea. The exercise included some of China's most modern warships and lasted nearly three weeks.