Wer wird China, Japan und Südkorea im Alter verteidigen?

Submission statement:

Fertility rates throughout East Asia are very low, even lower than in Western Europe. And drastically below the replacement rate of 2.1.

Soon, China, Japan and South Korea will all have fertility rates below 1.0. Their entire societies are greying rapidly. The populations of all three countries are declining every year, with Japan and South Korea already having had this problem for many years.

So the question is how will these countries‘ military and army handle this problem? Who will defend these nations in wars? They already have shortages when it comes to attracting young male recruits. This prolem will only exacerbate in the future. Robotics and AI might offer a partial solution, but things are not so clear cut.