How could a noble be both a lord and a vassle?

Answer 1

A noble is simply a man in power, that has been placed in charge of an area of land. Assuming it is in a feudal type state, he will have people who report to him, such as knights, and men who report to them, etc etc. Working their way down to the bottom, the serfs and peasants.

Being a vassal, he will be under the rule of a greater lord. an example would be Xerxes of the Persian empire. though he was solely in charge of his empire, he had many vassals beneath him, who were in charge of the areas of land that he conquered.

The advantages of being a vassal, is that you are often under the protection of a more powerful country of force, as you will technically be owned, or a part of the greater country. but at the cost of this, you are not independent and would have to pay taxes, goods, or fighting men to the ruler in return, and would not be able to take political direction, such as starting a war, without permission of the ruler.

Having vassals is a good way to annex country into an empire, without exterminating the local populace, as they become a part of your land, but they do retain their status as a country, so they will be less likely to resist overthrowing their ruler. Many countries used vassals as a good source of income in terms of goods and fighting men, and to keep the people they conquered happy. By allowing them to retain their identity.