Ever since Obama, the Japanese have been wrapping their minds around the idea that the US is not a credible defense partner anymore and have been quietly preparing for the time when they would have to go it alone.
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I worked on a naval facility in Japan for 2 years every day full time and was all over Japan during that timeframe. I traveled to Yokosuka, Itazuke, Sasebo, Nagasaki, Hiroshima, Osaka, and many other places. I worked with the Japanese all day every day. They entertained me and my wife in their homes. I daily observed the billions of dollars in facilities, equipment, ships and personnel that the US has committed to Japan for 77 years.
So, respectfully, I disagree with your statement highlighted above. The Japanese know the U.S. produces an idiot for President occasionally (Carter, Clinton, Obama and now Biden) and they just shift gears and ride it out. They do not and will not discontinue their militarily based dependency on the U.S. As my friend Yugi Kugita used tell me, almost daily, “Japanese love America”!!
Respectfully disagree. I am a US Navy veteran myself, spent three years at CNFJ in Yokosuka, and have lived in Japan for 35 years. I also have friends in the Japan Self Defense forces, a Japanese wife, daughter, and four grandchildren here.
The consensus I am seeing evolve says that while Japan certainly appreciates US support, they have come to the conclusion that they cannot always depend on it and that they must have a credible independent defense posture.
A quick look at the overview of the most recently released Japan Defense White Paper (https://www.ntv.co.jp/englishnews/articles/2021d4h133ib2t829bvd.html) makes it very clear to me that Japan is serious about upgrading its defenses and is preparing to meet the threat regardless of who is President of the USA.