What is the main idea of feudalism?

The main idea behind feudalism was to create a system in which along with land revenue, a standing army would be created for service. In other words feudalism was a system where the relationship in society was derived from the holding of land.

Feudalism in Europe is believed to have originated post the Dark ages, following the decline of the Roman Empire. It was the result of decentralization in the 8thc century when a lack of bureaucratic infrastructure meant that cavalry troops had to be hired without being allocated land.

For further reading check the following articles:

• Portuguese India
• British Raj
• Dutch Colonialism in India