Great empires often bankrupt themselves. Military supremacy is expensive.
You need expensive technology, maintaining far flung military bases, armies, navies, air forces, space forces, etc.
You either fund it by borrowing or taxing. There's a limit to both.
Directing economic resources to military spending instead of domestic brings eventual ruin.
Great Britain bankrupted itself in WW2. Once they lost their jewel India the sun set on the British Empire.
