Great analysis.
Demographics is destiny.
You didn't mention it but young people are far more effective soldiers than old people. So having very low fertility over a long period makes a country more vulnerable to invasion.
Russia had low fertility rates after 1989 too but during the Putin era they have risen significantly (but still below replacement).
Interestingly the other war in the news involves Israel, which has by far the highest fertility of any developed country (3.1) and Gaza which also has very high fertility.
The birth rate in Palestine was 5.44 in 2000, while today it is around 3.5. Compared to countries facing a population crisis, this is a high birth rate despite the state of war they are living in. Of course, there are many sociocultural and economic reasons underlying this. Restrictions in access to sexual protection and hygiene products and having a culturally multi-child family structure are some of them.
If we talk about Israel, unlike other countries, there is an increasing birth rate graph in the last 20 years. I think that Jews with high religious attachment are undoubtedly the ones who have the most share in the establishment of such a graph.
Patriotism and religious observance and the only way to maintain above replacement birthrates in the modern world.