Horns of a Dilemma

China poses threats to countries all around their border. In an ideal world, China would like to pick on one while the others watch, grateful they are lower down the (ever expanding) list of "core interests" to be brought into line. Japan and India are working to make sure China is less sure of that ability to isolate a target.

This is good:

Japan and India affirmed on Monday plans to strengthen their military cooperation amid rising tension in the Asian region.

Indian Defense Minister Arun Jaitley told his Japanese counterpart, Tomomi Inada, in Tokyo that his country hopes to pursue a strategic partnership with Japan for regional peace and stability.

On its own, this type of cooperation is not that much of a threat to China's freedom of action because India and Japan are far apart with the inability to project power far enough to directly help.

What makes this cooperation important is the friendship of America, which can give individual nations the confidence that they won't fact China alone because we knit together the defense capacities of otherwise isolated targets around China's periphery.

This affirmation to strengthen military cooperation indicates some level of confidence that America can be relied upon.

If that confidence holds up across the region, China can never be sure that concentrating power against one nation on their periphery won't be met by other nations at other points around their periphery. Ideally, that kind of uncertainty about being placed on the horns of a dilemma deters China from launching a war.