The U.S. decision to fly two B-52s through China's claimed "air defense identification zone" around a set of islands disputed between China and Japan (Senkakus/Diaoyus) was significant in several ways.
First, it was a blunt reminder that Northeast Asia remains the world's most combustible geopolitical hot spot.
Second, it's a strong signal that the Barack Obama administration is going to stand by its Asia-Pacific allies against Chinese aggression.