Murad, having already married Greek and Bulgarian…

Murad, having already married Greek and Bulgarian princesses, next incorporates into the rapidly expanding Ottoman empire many European vassals.

He retains local native rulers, who in return accept his suzerainty, pay annual tributes, and provide contingents for his army when required.

This policy enables the Ottomans generally to avoid local resistance by assuring rulers and subjects that their lives, properties, traditions, and positions will be preserved if they peacefully accept Ottoman rule.

It also enables the Ottomans to govern the newly conquered areas without building up a vast administrative system of their own or maintaining substantial occupation garrisons.