Until last year China put little effort of claim on the Senkaku Islands, owned by a family in Japan, treated to Japan after the war and used as a bombing range by the US military. But when the family sold the Islands and it's rights to Japan in 2012, China all of a sudden laid claim to the islands and are now including them in their protected territory, leading to the no fly zone. The net of it is China has claimed the islands used by the US military for bombing practice from Japan and it is a bad situation. It appears to me China now feels it has the strength to challenge our military and see if we back down appeasing them by giving them additional territory. I have not researched it, but I'd bet at this time of the year China is also due to have some sort of joint military exercise with North Korea. If so it will be a test of our ability to meet a two front challenge from the Chinese mainland.