Britain ordered assassination of India's Netaji Subhash Chandra Bose
O'Halpin said the assassination was ordered on March 7, 1941, when Bose was in hiding in Kabul after escaping virtual house arrest in Calcutta. The order was reconfirmed in June.
The assassination was to have been attempted in Turkey, a country Bose was expected to pass through on his way to Germany, O'Halpin said.
However, Netaji never went to Turkey. He reached Berlin via Moscow.
"As far as I know, he was the only significant political leader in any colony fighting British colonization who was explicitly targeted for assassination," O'Halpin said of the man who set up the Indian National Army to fight the British and who coordinated with the Axis powers during World War II.
"Now the reason he was targeted is because of his intentions to not simply lead India out of the empire but to do it by force and in conjunction with the Axis," the professor added.
Bose went missing in 1945, and the disappearance of the man known popularly as "Netaji," which means "leader" in Hindi, remains a mystery.