The Great Empire
At the height of the Roman Empire, Rome's influence reached as far north as Hadrian's Wall in present day England, as far south as Egypt, and as far east as present day Turkey,
Lebanon and Syria. To the ancient Romans they truly conquered the world. So how did the mighty Romans conquer so many people and bend them to the will of the empire, forcing Roman culture and way of life upon them? Well, they didn't really.
While it's certainly true that the Romans could fight and conquer foreign lands, they often really didn't have to. The Romans had a policy of letting people keep their own traditions and culture. In other words, instead of conquering an area, teaching them Roman ways and religion, and forcing their new people to be more "Roman" they merely made the conquered people swear fealty to Rome and then pretty much left them alone. This ended up being a wonderful strategy. Generally, a people will fight to preserve their way of life. But since being absorbed into the Roman Empire really didn't change much about a people's daily life many often gave up and willingly joined the empire rather than fighting.