Japan stepped up its role in large-scale war games with the United States this week, with one of its admirals commanding air and sea maneuvers that the U.S. military described as the most complex ever overseen by the Maritime Self-Defense Force.

The Keen Sword exercises involving more than 30,000 Japanese troops and 11,000 U.S. personnel come as Prime Minister Shinzo Abe seeks a higher profile for Japan in the security alliance.

At the same time, Washington has encouraged Tokyo to take a greater share of the defense burden, especially as China's military modernizes rapidly.