Though the recent geopolitical developments such as the withdrawal of US forces from Afghanistan, Russia-Ukraine war, China’s expansionism and influence operations, it seems that the world is moving back to the era of conflict between the state actors, terrorism emanating from the non-state terrorist groups, both national and transnational continues to be serious challenge to global peace and security. Over the last seven to eight decades, and terrorism has emerged as a major global threat. Particularly, in the 1980s in the wake of Soviet invasion of Afghanistan and the rise of Mujahidins supported by the US, terrorism has emerged has a truly transnational phenomenon with Pan-Islamist groups like Al Qaeda, Harakat Network and ISIS dominating the scene. India has been a victim of Pakistan-supported terrorism for the last three decades, mostly in the erstwhile state of Jammu and Kashmir (J&K), but not confined to J&K. An array of terrorist organizations, discussed in detail in this thesis, have been active in the Kashmir theatre since 1990; however, Jaish-e-Mohammad (JeM) presents a unique example of having brought India and Pakistan on the verge of a full-fledged conventional war twice, first in 2001 after JeM attacked the Indian parliament in Delhi and then in 2019, after a JeM fidayeen killed 40 Indian soldiers in a suicide attack. JeM, radical Deobandi terrorist organization with strong links to Al Qaeda, Taliban and Harakat network of terror groups, is known for its expertise in lethal fidayeen attacks. However, the organization remains underexplored in the academic world. As compared to other groups like Lashkar-e-Taiba and Hizbul Mujahidin, JeM has been a focus of a rigorous academic investigation because of the highly clandestine nature of the outfit and its brutal tactics against its adversaries. Also, unlike other terror groups of Kashmir, JeM has pan-India objectives. Having said the above, the JeM presents a major security challenge to India. Hence, I have investigated this organization in detail in this thesis exploring JeM’s origins, ideology, organisational structure, Kashmir operations, Pan-India operations, strategy, tactics and the future objectives. This thesis relies on the diverse variety of sources which include the interviews with the former and current JeM militants, financiers, intelligence professionals, journalists, and literature published in open sources such as journals, books, memoirs, media reports and literature derived from the intelligence and investigation agencies, such as the interrogation reports, intelligence briefs and charge sheets. In conclusion, I have argued that JeM is likely to continue and even strengthen as a major security threat to India in the future because of its historic ties with Al Qaeda and Taliban, and growing jihadi radicalization in India which can make young Muslim boys highly vulnerable to JeM recruiters.