This article describes dollar hegemony and the US military enforcement of it.
The reason why we invaded Iraq, had the JCPOA with Iran, and why we can't invade Iran.
The world's central banks were required to hold dollars.
This enabled the US to print money, and run up massive debt, abusing the situation.
Now this system is breaking, and its doubtful it will be restored.
Russia, China, India, and Japan are steadily selling off their dollar reserves.
The dollar will lose value, and the US debts likely cannot be paid.
Except with hyper inflated dollars.
https://www.counterpunch.org/2019/03/01/dollar-hegemony-again/
https://archive.fo/cCgPc