“We haven’t made the case to defend Taiwan,” insisted my friend, a Nagatacho insider.

Even though Taiwan has long been a prominent part of Japan’s security thinking, there hasn’t been a willingness to speak publicly about it. That is changing. Politicians and strategists have become more vocal about Taiwan’s place in Japanese security, making speeches on a regular basis and talking openly about the need to help defend Taiwan.

Making that case has become much more important as tensions climb in the Taiwan Strait and Japan debates a new defense budget, one that anticipates significant increases in spending. Yet for all the discussion of the need to be ready for a Taiwan contingency, there has been relatively little discussion of why Japan should be involved.