Called Super Cop, he has served twice as Director General of Police (DGP) Punjab, where he was credited with having brought the Punjab insurgency under control.

 

He was an author, editor, speaker, consultant on counter-terrorism, president of the Institute for Conflict Management and was president of the Indian Hockey Federation (IHF). 

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Gill wrote his first book Punjab: The Knights of Falsehood in 1997 (reprinted in 2008 in paperback), covering the Punjab insurgency. The book received positive reception in the Press and was deemed to provide a "great degree of authenticity" to the narrative of the events.

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Shri Gill was editor of the quarterly journal of the ICM, Faultlines: Writings on Conflict and Resolution and also wrote the ICM website, South Asia Terrorism Portal.

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He edited the 2001 book Terror And Containment: Perspectives on India's Internal Security with Shri Ajai Sahni. With Sahni, he also co-authored The Global Threat of Terror:Ideological, Material & Political Linkages.