I haven't done a deep dive through Capital vol. 1-3 yet so my understanding on this topic is limited, and I want to see if I have the basics down.
The core problem as I understand it is the tendency of the rate of profit to fall, because capitalism requires that not only do things stay profitable, but that the profits continually increase. This of course is impossible to sustain in a real, finite world.
Imperialism offers a way to delay the inevitable by opening up new markets and exploiting new supplies of labor and resources to keep profits increasing long after the imperialist power lost the ability to accomplish this domestically.
But as the rate of profit continues to fall, ever more aggressive expansion and exploitation is needed to maintain this growth, inevitably leading to conflict between capitalists to divide up the limited markets and resources in a competition to, if not be the winner, avoid being the biggest loser.
Losing access to these foreign markets and resources however starts to become an existential crisis for a capitalist state though, because the internal contradictions have been raised to such extremes that they could only be temporarily treated with imperialist exploitation, and if access to that exploitation is lost, complete and utter financial ruin for the bourgeoisie of that state follows.
So part of it is that the imperialist capitalist state, to preserve it's own existence, must fight increasingly desperately -- to the very brink of death -- over control of markets to expand into and resources to exploit, correct? Because otherwise, the whole decrepit system comes crashing down?
But also, there's an aspect of war itself creating new markets to exploit, isn't there? An orgy of destruction and death creates a market for weapons, and new opportunities for exploitation in rebuilding and redividing the rubble? If that's the case, is eternal global war a possible solution to the problems of capitalism? Can a cycle of destruction and rebuilding keep the whole rotten wheel turning indefinitely until the whole planet is poisoned and exhausted of resources? Or do the unsustainable demands of capitalism somehow ensure that the war must spread and intensify to the point of total annihilation?
As a tangential point, could imperialism hypothetically stave off its death a bit longer by becoming interplanetary?
I know I'm missing some big points in here, please fill me in, even though this is all very broad strokes and oversimplified. And if anyone has reading on the subject that's more approachable than Capital (a pretty low bar), I'd love to read it.