Read history from the Franco-Prussian War in 1870 onwards. It was a time when the previously dominant Great Britain and Austria Hungary slide into economic troubles, and their fortunes declined due to competition, huge military expenditures, and increasingly sclerotic political institutions. There was huge inequality in London and Vienna, ranging from the hovels in the slums to the great houses of the nobility and bourgeosie.

It all led to WW I and the period from 1914 to about 1949 and the end of the Chinese revolution, during which about 200 million soldiers and civilians died from war, revolution, purges, disease (Spanish flu epidemic), and starvation (e.g. in India).

I'd expect the next episode to start in about 2030. And probably multiple billions of casualties during the subsequent decades.