The National Security Guard (NSG), popularly known as Black Cats, is India's elite federal counter-terrorism force established in 1984 under the National Security Guard Act. NSG operates under the Ministry of Home Affairs and is deployed for hostage rescue, counter-terrorism operations, VIP security in high-threat environments, neutralizing IEDs, and anti-hijacking operations. The Special Action Group (SAG) is the operational/assault wing of NSG, composed exclusively of personnel deputed from the Indian Army. SAG commandos are among the world's most highly trained counter-terrorism operatives, comparable to US Delta Force and British SAS.

NSG SAG personnel are selected on deputation from the Indian Army — they must be serving Army personnel (NCOs and Officers) with an exceptional service record. The selection process is among the most demanding in India: initial fitness screening (5 km run in under 18 minutes, 30+ push-ups in 2 minutes, 30+ sit-ups in 2 minutes, 6+ chin-ups), NSG selection course (100-day course with continuous physical and psychological tests, obstacle courses, live firing, and tactical exercises), and psychological profiling. The overall selection rate is reportedly less than 10% of those who attempt the course.

NSG SAG training is designed to create the highest-quality counter-terrorism operatives. The 100-day selection course includes: Extreme physical conditioning (running 20+ km daily with full combat load, obstacle courses, swimming), Combat skills training (CQB — Close Quarters Battle, hostage rescue drills, sniper training), Special operations skills (fast rope, para-jumping, diving, covert entry techniques), Psychological stress training (sleep deprivation, isolation, high-pressure decision making), and Live exercises (actual hostage rescue simulations with live ammunition). Post-selection, NSG personnel receive ongoing advanced training, including exchanges with elite units of USA, UK, Israel, and Germany.

The Special Ranger Group (SRG) is the NSG component recruited from Central Armed Police Forces (CAPFs) — primarily CRPF, BSF, CISF, ITBP, and SSB. While SAG handles offensive counter-terrorism operations, SRG is responsible for security and protective cover for the NSG operations including perimeter security, logistics support, and VIP protection tasks. SRG personnel undergo a rigorous selection and training process (though less intense than SAG) and are considered elite within their parent CAPF. Serving in NSG on deputation is a mark of distinction for CAPF personnel.

NSG's most famous operation is Operation Black Tornado — the 26/11 Mumbai attack response from November 26-29, 2008. NSG SAG commandos flew from Delhi and conducted storming operations at the Taj Mahal Hotel, Trident Hotel, and Nariman House simultaneously, neutralizing armed terrorists who had been trained for sustained urban warfare. The operation demonstrated SAG's capability in multi-location urban counter-terrorism under media glare and political pressure. NSG also led Operation Ashwamedh (IED neutralization), provided personal security for former PM Rajiv Gandhi, and handled numerous aircraft hijacking responses. The NSG pays are enhanced by 25-30% over parent service pay during deputation.