Forgive my ignorance, but how does a country with a strong military turn that into GDP? I don't understand how military > manufacturing in terms of GDP. In my mind, manufacturing > military, but my knowledge of economics isn't great.
For example the opium wars.
Nowadays the empire works via its currency that allows it to buy real goods and assets for something it can create for free with little constrain.
Of course the exploitive nature of the “exorbitant” privilege is controversial; and some economists would argue that it does not exist at all.
For a more recent example, the CIA operations on South and Central America in the 20th century. But well, it didn't take the entire military there, just a military-like paragovernamental entity.
Doing that today would be seen in a bad light and has a real chance of turning the entire world against the country. That doesn't seem enough to stop Russia, though.
Malinvested money will pump GDP for a few years before growth stops and potentially reverses.