In 1965, Captain Manmohan Singh Kohli, an officer in the Indian Navy and one of the country's best mountaineers, went on an arduous trek of 125 km. But this was no routine mountaineering expedition.

Koli was leading a group of Central Intelligence Agency and Intelligence Bureau officials on a covert mission to the Himalayas to spy on China’s nuclear capability after a nuclear test there the previous year.

The plan was to install a six-foot antenna at the top of the Nanda Devi, to pick up communication signals from across the border from China. The set-up was powered by plutonium fuel. The mission was a tall order by any measure.

A month into the arduous trek, at the fourth and final camp, just 300 metres away from the summit, a blizzard forced members of the expedition to change course. They left some of their equipment behind to enable a hasty retreat to safety, intending to come back the next year and pick up from where they left off. However, when they came back in June 1966, the equipment was all gone – including the prized plutonium, a radioactive element that could have potentially disastrous consequences in the wrong hands.

The abandoned mission came back into the news after a leak in the 1970s, when questions were raised in Parliament about the dangers of the lost plutonium.

In this episode of The Intersection, Samanth Subramanian revisits the mission and speaks to journalist Vinod Jose, who authored a story on this expedition in The Caravan about this fascinating story and why there were no further attempts to find the lost plutonium.

This is the latest episode of The Intersection, a fortnightly podcast on Audiomatic. For more such podcasts, visit

Correction and clarifications: This article was edited to correct the name of the mountain that was the focus of this operation.