Answer:
tributary
Explanation:
In a tributary system, a certain empire / territory that was defeated during a battle will be forced to work on behalf of the conqueror unless they want to face executions/destructions.
Tributary system was a very popular practice in the age of Empires, Even the European colonization can be considered as some form of Tributary. This practice ended around 1800s as more countries started to transitioned into democracy and prefers to resolve their conflicts through trades and agreements.
