(CNN) Winston Churchill's policies caused a famine that claimed more than 3 million Indian lives, according to a new study using soil analysis for the first time to prove the origins of the disaster.

The 1943 Bengal famine was the only famine in modern Indian history not to occur as a result of serious drought, states the report, which was conducted by researchers in India and the United States.

"This was a unique famine, caused by policy failure instead of any drought," Vimal Mishra, the lead researcher and an associate professor at the Indian Institute of Technology Gandhinagar, told CNN.

Researchers used weather data to gauge the amount of moisture in the soil during six major famines in the subcontinent between 1870 and 1943.

"There have been no major famines since independence," said Mishra. "And so we started our research thinking the famines would have been caused by drought due to factors such as lack of irrigation."

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