The only example of successful intervention is the Roman one. Everyone else failed. This includes the British, the Persians, and Russians, all of whom had powerful empires of relatively brief duration.
How does one build an empire that lasts a thousand years? One starts by studying the Romans, whose Republic was the model for the government of the United States. Are you still with me?
- Had perfect belief in their power, cultural superiority, and moral rightness
- Had sufficient wealth to build a great army and navy
- Had sufficient population of men willing and able to fight
- Had outstanding leadership in the army and navy, and ability to promote from within the ranks
- Had an army that could dominate populations through its exertion of threat and highly organized professional and technical capability
- Had a well established bureaucratic program for subsuming conquered lands into the empire
- Had no qualms about meting out the severest punishment in order to promote its agenda of stability and submission to Rome
That, my dears, is how it's done.