Step 1: Background.
This question is from the chapter "Indigo" by Louis Fischer, which describes Gandhi's Champaran movement.
Step 2: Reason for compensation.
The British planters had long forced peasants to cultivate indigo on 15% of their land under the exploitative "sharecropping system".
Step 3: The pretext.
When synthetic indigo was invented in Germany, demand for natural indigo fell. The landlords decided to release the peasants from the contract but demanded compensation for doing so.
Step 4: Conclusion.
Thus, the planters falsely claimed that peasants must pay them compensation for giving up indigo cultivation.
Final Answer: \[ \boxed{\text{Planters demanded compensation as peasants were being released from indigo contracts.}} \]