Julious Ceasar offered shares the seized land as a reward to his officers. Ghengis Khan relied on intimidation, initially starting with a few men and once he'd conqured Mongolia (which many had tried and failed to do before) people began to fear and respect the army for that achievement and thus wouldn't go against it; Ghengis Kahn also relied less on a huge number of men and more on weaponry, he was likely the first ruler in history to use biologic warfare and he invented a device where a gun powder (which at that time only tiny handful of nations knew how to create) was put at the bottom of a box which was then dilled with arrows which were set on fire and then launched into the enemy city. One of the gods worshiped by the Romans was a war god. Ghengis Kahn's empire allowed a surprising level of religious freedom and many of his people thus worshiped a war god as well.