By appointing a great number of local governors and travelling overseeers. The feudal system meant that his knights were rewarded with land for serving him loyally to govern in return for their continued loyalty. Also, in that day and age the Court had to live off what the local area and crops could provide. A big Court like Charlemagne's could therefore never stay long in one place and it was regularly on the move to temporarily settle in another place in the Empire. Even if this happened by necessity, Charles didget around much in his realm.
their religion
There were two causes of the fall of the Roman Empire. They were internal and external. Internally, the Roman Empire became weaker and weaker. It started pulling back from its frontier territories. It abandoned England. Germanic tribes moved into the Empire and carved out their own areas. They cut back on taxes. Finally Pippin did not pay taxes and ended the control of the empire in North West Europe. The Arabs conquered the lands held by the empire in the Eastern Mediterranean, North Africa, and Spain. The Huns carved out Hungry. So, first the Empire cut back its size. Then it could not keep the barbarians from carving out their areas within the empire. Then it could not keep others from reducing its borders.
To keep the holy land out of Muslim control.
They need to be powerful and popular with their country. They also need to be aggressive and to keep control.
Laws were one of the factors that gave the empire unity. Since all provinces and territories were ruled by Roman law, the laws were the glue that held the empire together.
Charlemagne travelled around the empire frequently and extensively.
Pretty much all of it. It was instrumental to keep Texas out of the war and to control the western territories.
Assyrians needed a strong army to keep the people they conquered in control. They also needed one to conquer more people and protect their land.
William the Conqueror split up the land into territories and gave a piece of land to knights that had always remained noble to him. He ordered them to control their territory and kill those that stood in the way.
They allowed the conquered people to keep their religous beliefs.
their religion
the Incas allowed the conquered people keep their religious beliefs
Guam and Puerto Rico remain US Territories.
Indochina
No one- the humans got to keep it.
Alexander The Great
haider Mongol rulers did however rule with some tolerance allowing conquered people to keep their religions