India, May 14 -- In a modest chamber with a high ceiling, inside one of the most secure offices in India, in a white- walled room on first floor of the imposing South Block, a phone sits atop a table.

It is always manned, sometimes by a major, and at other times by a lieutenant colonel, top officials told HT on Tuesday.

No one else accesses the phone.

The moment he picks up the receiver, another phone rings 700 km away in the Pakistan Army headquarters in Rawalpindi and is answered by a duty officer on the other end of the line, they said, asking not to be named. And when the phone rings, it means someone in the Rawalpindi HQ has picked up their phone.

This is no ordinary phone.

It is the hotline between the Indian Army's director ge...