Defence Technology — Missiles, Nuclear Doctrine, DRDO & Indigenisation

Overview

Defence Technology is a high-yield topic for UPSC Prelims (factual questions on missiles, organisations, tests) and GS3 Mains (security challenges, indigenisation, technology). Questions often appear in the context of current affairs — a successful missile test or a new defence policy typically triggers a question in the next cycle.

Key areas: DRDO and its projects, India's missile programme, nuclear doctrine and deterrence, anti-satellite capability, and defence indigenisation initiatives.

DRDO — Defence Research and Development Organisation

Establishment and Structure

Key DRDO Projects

India's Missile Programme

Integrated Guided Missile Development Programme (IGMDP)

Launched in 1983 under the leadership of Dr APJ Abdul Kalam at DRDO, the IGMDP aimed to develop five indigenous missile systems: Prithvi, Agni, Trishul, Akash, and Nag. The programme was formally concluded in 2008 after successfully achieving its objectives, though development of advanced variants continues.

Mnemonic: "PATAN" — Prithvi, Agni, Trishul, Akash, Nag — the five original IGMDP missiles. This is one of the most frequently tested facts in Prelims.

Comprehensive Missile Table

Ballistic Missiles

Submarine-Launched Ballistic Missiles (SLBMs)

Cruise Missiles

Air Defence and Tactical Missiles

Exam Tip: UPSC often frames questions as "Which of the following statements is/are correct?" about missile characteristics. Remember: Agni-V is three-stage, solid-fuelled, canisterised, and was tested with MIRV capability (Mission Divyastra, 2024). BrahMos is supersonic (not subsonic or hypersonic) and is a joint India-Russia venture.

Nuclear Doctrine

India's Nuclear Tests

Key Elements of India's Nuclear Doctrine

India's nuclear doctrine was outlined through a Draft Nuclear Doctrine (1999) and formalised via a Cabinet Committee on Security (CCS) press release on 4 January 2003. The principal elements are:

1. No First Use (NFU): India will not be the first to use nuclear weapons. Nuclear weapons will only be used in retaliation against a nuclear attack on Indian territory or Indian forces anywhere.
2. Credible Minimum Deterrence: India maintains the minimum number of nuclear weapons necessary to inflict unacceptable damage in a retaliatory strike.
3. Massive Retaliation: Nuclear retaliation to a first strike will be massive and designed to inflict unacceptable damage.
4. Non-use against non-nuclear weapon states: India will not use nuclear weapons against states that do not possess them.
5. Chemical/Biological caveat: The 2003 operationalisation press note added that nuclear weapons could be used if Indian forces are attacked with biological or chemical weapons.
6. Civilian control: The authority to order a nuclear strike rests with the elected civilian leadership — specifically, the Prime Minister through the Nuclear Command Authority.

Nuclear Command Authority (NCA)

Nuclear Triad

India completed its nuclear triad — the capability to deliver nuclear weapons from land, air, and sea — with the commissioning of INS Arihant and its first deterrence patrol (announced November 2018).

Anti-Satellite (ASAT) Test — Mission Shakti

Defence Indigenisation

Make in India in Defence

The government has progressively increased the share of domestic procurement in the defence budget — from 54% in 2018–19 to 68% by 2021–22, with 25% of the procurement budget earmarked for the private sector.

Defence Acquisition Procedure (DAP) 2020

Unveiled by Raksha Mantri in September 2020, the DAP 2020 replaced the earlier Defence Procurement Procedure (DPP). Its highest preference goes to the Buy (Indian-IDDM) category — Indigenously Designed, Developed and Manufactured — and Buy Global is permitted only in exceptional cases with approval of the Defence Acquisition Council (DAC) or Raksha Mantri.

Positive Indigenisation Lists

The Ministry of Defence has notified multiple Positive Indigenisation Lists since 2020, progressively banning the import of defence items that must be sourced domestically:

Key Indigenisation Platforms and Initiatives

Common Mistake: Students often confuse iDEX with DISC. Remember: iDEX is the umbrella framework for defence innovation; DISC (Defence India Start-up Challenge) is a specific programme conducted under iDEX to identify and fund start-up solutions.

Cross-paper relevance

• GS3 — Science-Technology (primary) — DRDO projects (Tejas Mk-1A delivery Aug–Sep 2026, Mk-2, AMCA, Zorawar, Kaveri); missile programme (Agni, BrahMos, Akash, Nagastra, long-range hypersonic Nov 2024, ET-LDHCM Jul 2025, LR-AShM Phase-II May 2026, scramjet 1,200-sec test May 2026, ULPGM-V3 May 2026); Operation Sindoor as live validation of indigenous defence technology; S-400 first combat use
• GS3 — Economy — Defence manufacturing: Atmanirbhar Bharat, ₹38,424 crore defence exports FY26 (record; 62.66% growth), private sector share, Make in India in defence
• GS3 — Internal Security — Security capabilities: Operation Sindoor (7–10 May 2025) — first India–Pakistan direct strike since 1971; Akashteer AI-enabled air defence network; anti-drone systems; loitering munitions (Nagastra-1, SkyStriker)
• Essay — Recurring theme: "Atmanirbhar Bharat in defence — aspiration and achievement"; "India's strategic autonomy through self-reliance"; "Operation Sindoor: technology, doctrine, and deterrence"

Recent Developments (2024–2026)

India's Defence Exports — ₹23,622 Crore in FY 2024–25 (Superseded by FY26 record below)

India's defence exports reached ₹23,622 crore (approximately $2.8 billion) in FY 2024–25, which was itself a record at the time — reflecting over 30-fold growth in a decade. Key products: BrahMos cruise missiles (Philippines), Pinaka multi-barrel rocket systems (Armenia), ATAGS, Akash air defence missiles, ammunition, armoured vehicles, fast-attack vessels, and electronics. The private sector contributed ₹15,233 crore (64%) and DPSUs contributed ₹8,389 crore (36%) in FY25.

Note (May 2026): The FY24-25 figure of ₹23,622 crore has been surpassed by the FY25-26 record of ₹38,424 crore — see the FY26 entry below. Use the FY26 figure as the current benchmark; the FY25 figure is useful for tracking the year-on-year growth trajectory (62.66% jump).

UPSC angle: The FY25 figure (₹23,622 crore) is now historical context; the operative current figure for Prelims 2027 and Mains 2026 is ₹38,424 crore (FY26). Know both for trend analysis.

Mission Divyastra — MIRV Capability (11 March 2024)

India successfully conducted the maiden flight test of Agni-V with MIRV (Multiple Independently Targetable Re-entry Vehicle) technology on 11 March 2024 from Abdul Kalam Island, Odisha. Code-named Mission Divyastra, the test demonstrated Agni-V fitted with multiple warheads, each independently targetable. India became the sixth country with confirmed MIRV capability (after USA, UK, Russia, France, China).

Agni-V (range: 5,000–8,000 km; three-stage solid-fuelled; canisterised; ICBM-class) is now MIRV-capable. This significantly enhances India's deterrent against China by increasing the complexity of any adversary's anti-ballistic missile defence — a country would need to intercept multiple warheads rather than one.

UPSC angle: Mission Divyastra (11 March 2024), Agni-V MIRV, sixth country with MIRV capability, nuclear deterrence implications, and No First Use doctrine — Mains GS-3 content.

Operation Sindoor — India's Indigenous Defence Tech Demonstrated (May 2025)

In response to the Pahalgam terror attack (22 April 2025) in which 26 civilians were killed by Lashkar-e-Taiba-linked militants, India launched Operation Sindoor — precision strikes on nine terrorist launchpads across Pakistan and Pakistan-occupied Kashmir — in the early hours of 7 May 2025 (strike phase completed in under 23 minutes). Pakistan retaliated with drone and missile attacks on 9–10 May 2025; a ceasefire was announced on 10 May 2025.

Weapon systems used in strike phase:

• BrahMos supersonic cruise missiles (DRDO-NPO joint venture) — used for precision strike
• SCALP and HAMMER precision weapons (French-made, Rafale-delivered)
• SkyStriker loitering munition — produced by Bengaluru-based Alpha Design Technologies with Israel's Elbit Systems; 5–10 kg warhead, 100 km range; operational debut
• Nagastra-1 loitering munition — specifically noted by Defence Minister Rajnath Singh as used extensively

Indigenous air defence systems:

• Akash SAM (DRDO): intercepted Pakistani drones and missiles
• Akashteer (BEL): AI-enabled automated Air Defence Control and Reporting System — integrated Akash, QRSAM, 3D tactical radars, and naval systems into a single tri-service network; described as "a global first" in interoperability
• QRSAM (Quick Reaction Surface to Air Missile, DRDO)
• D4 anti-drone system (indigenous)
• S-400 ("Sudarshan Chakra") — tracked 300+ Pakistani drones and missiles; intercepted 95% within its 400 km kill zone; achieved the longest-range kill at ~315 km during the engagement; first-ever combat use of the S-400 system by India; also reportedly engaged Pakistani AWACS-type electronic warfare aircraft
• MR-SAM (Indo-Israeli): engaged cruise missiles and UAVs

Significance for UPSC Science & Technology: Operation Sindoor was the first live operational validation of India's integrated indigenous air defence architecture, loitering munitions capability, and precision strike doctrine under contested airspace conditions. The performance of Akash, Akashteer, and Nagastra-1 directly strengthens the Atmanirbhar Bharat in defence narrative.

UPSC angle: Operation Sindoor (7–10 May 2025) is the most significant Prelims 2027 and Mains 2026 current affairs event in the defence technology domain. Key facts: trigger (Pahalgam attack, 22 April 2025), targets (9 terror camps in Pakistan/PoK), weapons (BrahMos, Akash, Akashteer, Nagastra-1, SkyStriker), indigenous systems' battlefield debut, and the first India–Pakistan direct strike since 1971 on Pakistani Punjab province.

AMCA — India's 5th-Generation Stealth Fighter Programme

The Cabinet Committee on Security (CCS) approved the Advanced Medium Combat Aircraft (AMCA) programme in March 2024 at ₹15,803 crore for prototype development. AMCA is India's first indigenous 5th-generation stealth fighter, developed by Aeronautical Development Agency (ADA) with HAL for production.

Progress since March 2024:

• Full-scale engineering model displayed publicly at Aero India 2025 (February 2025, Bengaluru)
• ADA is in a 24-month detail design phase (from April 2024, ongoing)
• Three private sector consortia shortlisted for prototype manufacturing (Tata Advanced Systems; L&T–BEL; Bharat Forge–BEML–Data Patterns); tenders expected mid-2026
• 600 acres at Puttaparthi Airport, Andhra Pradesh, cleared for ADA/AMCA use (May 2026)
• Prototype rollout target: late 2026/early 2027; first flight target: 2028; certification: 2032; induction: ~2034
• Engine: Mk-1 prototype will use GE F414-GE-INS6; Mk-2 will use a new 120 kN-class engine co-developed with France's Safran (10-year programme)

Zorawar Light Tank — High-Altitude Warfare (2024–2026)

The Zorawar Light Tank (jointly developed by DRDO and L&T) was unveiled in July 2024 and completed developmental field firing trials at Mahajan Field Firing Range, Bikaner in September 2024 (desert terrain). High-altitude trials at Nyoma, Ladakh (4,200+ m) were completed in December 2024; the Nag Mk-II anti-tank guided missile was successfully test-fired from Zorawar (late 2025). Army user trials commenced 2026, with results pending.

Zorawar weighs approximately 25 tonnes — lighter than the Arjun (59 tonnes) — and is air-transportable by IL-76. Designed for Ladakh/Arunachal high-altitude terrain where heavier tanks cannot operate. Initial order: 59 tanks; larger follow-on order of ~350 planned post-trials.

UPSC angle: AMCA (5th-gen stealth fighter, March 2024 CCS approval ₹15,803 crore, first flight 2028), Zorawar (high-altitude light tank, 25 tonnes, user trials 2026), and the DRDO-private sector partnership model (ADA-HAL-Tata; DRDO-L&T) are Prelims and Mains data points on indigenisation.

Integrated Drone Detection and Interdiction System (IDD&IS)

The Indian Army inducted the first batch of the Integrated Drone Detection and Interdiction System (IDD&IS) in March 2024, addressing the emerging threat of armed drones and drone swarms — as demonstrated extensively in the Russia-Ukraine and Israel-Gaza conflicts. IDD&IS uses radar, electro-optical sensors, RF detection, and jamming to detect and neutralise hostile drones in critical zones.

DRDO's Counter-Drone Technology Centre has developed a range of counter-UAS systems including Indrajaal (area denial system for large areas), D4 (Drone Detect, Deter, Destroy) system, and SkyFence electronic jamming systems. The conflict in Ukraine demonstrated that drone countermeasures are now as essential as traditional air defence, making this a rapidly growing defence technology priority.

UPSC angle: Counter-drone technology, IDD&IS induction, DRDO counter-UAS systems, and the lessons from Ukraine for Indian defence technology are Mains GS-3 content.

MQ-9B Predator Drone Acquisition (October 2024)

India signed a $4 billion defence deal with the United States on 15 October 2024 to acquire 31 MQ-9B Predator drones manufactured by General Atomics. The deal was formalised in New Delhi during US Secretary of Defense Austin's visit.

UPSC angle: Prelims — MQ-9B deal: 31 drones, $4 billion, signed 15 October 2024; SeaGuardian (15) for Navy; SkyGuardian (16) split for Army and IAF; MRO facility in India. Mains — evaluate the strategic significance of the MQ-9B deal for India's ISR capabilities and Quad alignment; assess the role of defence acquisitions vs domestic R&D in building military capability.

DRDO's Hypersonic Missile — First Long-Range Test (November 2024)

DRDO successfully conducted the maiden flight trial of India's first long-range hypersonic missile on 16 November 2024 from Dr APJ Abdul Kalam Island, Odisha. The missile, indigenously developed by the APJ Abdul Kalam Missile Complex (Hyderabad) with multiple DRDO laboratories and industry partners, demonstrated the following:

• Speed: greater than Mach 5
• Range: greater than 1,500 km
• Capability: can carry conventional and nuclear payloads
• Terminal accuracy: confirmed via down-range ship stations

Defence Minister Rajnath Singh described the test as a "historic achievement" placing India in the select group of nations (USA, Russia, China, previously) with operationally validated long-range hypersonic strike capability. Unlike tactical hypersonic glide vehicles, this is a strategic-range system.

UPSC angle: India's first long-range hypersonic missile test (16 November 2024, >1,500 km, DRDO/Kalam Missile Complex) is a Prelims 2027 data point. The distinction between hypersonic glide vehicle (HGV — re-entry glide after ballistic launch, e.g., Russia's Avangard) and hypersonic cruise missile (air-breathing scramjet, e.g., BrahMos-II under development) is a UPSC concept distinction worth knowing.

India's Hypersonic Missile Programme — 2025–2026 Milestones

Following the first long-range hypersonic missile test in November 2024, India's hypersonic programme has advanced significantly across multiple tracks in 2025–26:

ET-LDHCM (Extended Trajectory-Long Duration Hypersonic Cruise Missile) — flight-tested July 2025: DRDO successfully conducted a flight test of the ET-LDHCM in July 2025, with the missile achieving its intended trajectory and hitting its target with precision. The system operates at speeds exceeding Mach 5 and maintains structural integrity at temperatures above 2,000°C during hypersonic flight (APJ Abdul Kalam Missile Complex / DRDL).

LR-AShM (Long-Range Anti-Ship Missile) — Phase-II Trial, 1 May 2026: DRDO conducted a Phase-II trial of India's Long-Range Anti-Ship Hypersonic Missile (LR-AShM) on 1 May 2026 off the Odisha coast. The missile struck a simulated sea-borne target at a range of 1,500 km, validating terminal guidance precision and sustained high-velocity flight at hypersonic speeds. DRDO Chairman Samir V. Kamat confirmed in April 2026 that full trials are imminent (Business Standard, April 2026).

Scramjet engine breakthrough — 1,200-second test, May 2026: DRDO's Defence Research and Development Laboratory (DRDL) achieved a critical milestone on 11 May 2026 when it successfully ran an actively cooled full-scale scramjet combustor continuously for over 1,200 seconds (20 minutes) — a world-class endurance benchmark for air-breathing hypersonic propulsion. This follows an earlier 12-minute (720-second) ground test in January 2026 and a subscale test in April 2025. A scramjet (supersonic combustion ramjet) is the propulsion system for sustained hypersonic cruise missiles (unlike hypersonic glide vehicles which are unpowered after launch). India is now among the very few countries with demonstrated long-duration scramjet capability (PIB, 11 May 2026; The Week, 11 May 2026).

UPSC angle: India's hypersonic programme now spans multiple concurrent tracks — ET-LDHCM (flight-tested July 2025), LR-AShM (Phase-II trial May 2026, anti-ship, 1,500 km), and scramjet engine (1,200-sec test May 2026). Together with the November 2024 long-range test, India has established comprehensive hypersonic capability. Key concept distinction for Prelims 2027: ballistic hypersonic (rocket-boosted, glide at Mach 5+, e.g., DRDO's November 2024 missile) vs. scramjet-powered hypersonic cruise (air-breathing, sustained flight, e.g., BrahMos-II / ET-LDHCM class) — fundamentally different propulsion technologies.

DRDO ULPGM-V3 — UAV-Launched Precision Guided Missile (May 2026)

DRDO completed the final development trials of the Unmanned Aerial Vehicle Launched Precision Guided Missile (ULPGM)-V3 on 18–19 May 2026 at the DRDO test range near Kurnool, Andhra Pradesh — in both air-to-ground (anti-tank) and air-to-air (anti-drone, anti-helicopter) modes.

Key features:

• Platform: Integrated with UAVs developed by Newspace Research and Technologies, Bengaluru
• Development partners: Bharat Dynamics Limited (BDL) and Adani Defence Systems & Technologies Limited
• Control: Integrated Ground Control System (GCS) for remote command
• Significance: First Indian drone-launched guided missile with dual air-to-ground and air-to-air capability; directly addresses lessons from Ukraine/Gaza where drone-launched precision weapons became decisive

Following successful development trials, ULPGM-V3 will proceed to production readiness and induction into the Indian Armed Forces.

UPSC angle: ULPGM-V3 (UAV-launched, dual-mode, May 2026 final trials, BDL + Adani Defence partnership) represents the fusion of India's drone warfare and precision munitions capability — a GS3 Science & Technology + Atmanirbhar Bharat data point for Prelims 2027.

India's Defence Exports — ₹38,424 Crore Record in FY 2025–26 (April 2026)

India's defence exports reached an all-time high of ₹38,424 crore (approximately $4.6 billion) in FY 2025–26 — a 62.66% jump over FY 2024–25's previous record of ₹23,622 crore, and more than 25-fold growth from ₹1,521 crore in FY 2016–17. India exported to over 80 countries, with the number of exporting companies rising to 145 (from 128 in FY25, a 13.3% increase). Crucially, DPSUs (Defence Public Sector Undertakings) led for the first time, contributing ₹21,071 crore (54.8%), while the private sector contributed ₹17,353 crore (45.2%) — a shift from previous years when private sector led.

Key export products include BrahMos cruise missiles (Philippines, with more Asian buyers in pipeline), Pinaka Multi-Barrel Rocket Launcher systems, Akash Surface-to-Air Missile systems, Advanced Towed Artillery Gun System (ATAGS), Light Combat Helicopter, ammunition, armoured vehicles, and fast patrol vessels. The government's target remains ₹50,000 crore in defence exports by 2028–29, with the FY26 achievement placing India well on track.

UPSC angle: FY26 defence export record (₹38,424 crore, 62.66% growth, 80+ countries, 145 exporters), DPSU-led shift, BrahMos as flagship export, and the ₹50,000 crore 2028–29 target are high-priority Prelims and Mains GS-3 data points.

Important for UPSC

Prelims Focus Areas

• Names, ranges, and types of missiles (especially Agni series, BrahMos, K-series SLBMs)
• DRDO: establishment year (1958), key labs and projects
• Mission Shakti: year (2019), India became 4th ASAT nation
• Nuclear tests: Pokhran-I (1974, Smiling Buddha), Pokhran-II (1998, Operation Shakti)
• IGMDP: launched 1983, led by Dr APJ Abdul Kalam, five missiles (PATAN)
• Defence indigenisation initiatives: iDEX, SRIJAN, Defence Industrial Corridors (UP and TN)
• Long-range hypersonic missile first test: 16 November 2024, >1,500 km, DRDO/Kalam Missile Complex
• ET-LDHCM: Extended Trajectory-Long Duration Hypersonic Cruise Missile; flight-tested July 2025; sustains Mach 5+ at 2,000°C
• LR-AShM: Long-Range Anti-Ship Hypersonic Missile; Phase-II trial 1 May 2026, Odisha coast, 1,500 km range
• Scramjet engine test: DRDL Actively Cooled Full-Scale Scramjet Combustor — 1,200-second (20-minute) continuous run, May 2026 (world-class endurance benchmark)
• ULPGM-V3: UAV-launched precision guided missile, final trials completed 18–19 May 2026 (Kurnool), dual air-to-ground and air-to-air modes
• Tejas Mk1A: 15+ airframes ready; first IAF delivery targeted August–September 2026 (F404 engine supply contingent)

Mains Dimensions (GS3 — Internal Security / Science & Technology)

• Strategic deterrence: Evaluate the effectiveness of India's No First Use doctrine and credible minimum deterrence in the current geopolitical context
• Indigenisation vs imports: Analyse the trade-offs between self-reliance and operational readiness. Discuss the role of DAP 2020 and positive indigenisation lists
• Technology self-reliance: Examine how initiatives like iDEX, DISC, and Defence Industrial Corridors contribute to Atmanirbhar Bharat
• Emerging threats: Hypersonic missiles, space warfare (ASAT), cyber warfare — new frontiers of defence technology

Interview Angles

• Should India revise its No First Use policy?
• How can India balance the need for cutting-edge technology with budget constraints?
• The role of private sector and start-ups in defence manufacturing

Current Affairs Connect

Defence technology is a frequently tested current affairs topic. New missile tests, defence deals, indigenisation milestones, and policy changes appear regularly in Prelims and Mains.

Stay updated with the latest defence developments on Ujiyari.com — our complementary current affairs portal covers defence news with UPSC-specific analysis.

Vocabulary

Ballistic

• Pronunciation: /bəˈlɪs.tɪk/
• Definition: Relating to projectiles that move under their own momentum, gravity, and aerodynamic drag after an initial powered phase, following a curved trajectory without sustained propulsion.
• Root: Greek ballein (to throw) → Latin ballista (siege engine for throwing) + -ic; missile sense from 1949.
• Origin: From Latin ballista ("a military siege engine for throwing stones") + -ic, ultimately from Greek ballein ("to throw"); first used in English in the mid-18th century, with the missile-related sense emerging in 1949.
• Part of Speech: adjective
• Word Family: ballistic (adj), ballistics (n), ballistician (n), ballistically (adv), antiballistic (adj)
• Usage: India's induction of submarine-launched ballistic missiles has fundamentally recalibrated the subcontinent's deterrence calculus, furnishing a credible second-strike capability that underpins its declared no-first-use doctrine.
• Synonyms: projectile, missile-borne, propulsive, trajectory-based, kinetic
• Antonyms: guided, propelled, stationary, controlled
• Mnemonic: Think of a BALL thrown hard — the Greek root "ballein" means "to throw"; a ballistic object follows the arc of a hurled ball, and an angry person "thrown" into a rage "goes ballistic".

Supersonic

• Pronunciation: /ˌsuː.pəˈsɒn.ɪk/
• Definition: Travelling at a speed greater than the speed of sound in the same medium (approximately 343 metres per second or Mach 1 in air at sea level).
• Root: Latin super- = above + sonus = sound + -ic = adjectival suffix; first recorded 1919
• Origin: From Latin super- ("above") + sonus ("sound") + -ic; first recorded in 1919, originally meaning "relating to sound waves beyond human hearing," but by 1934 it described speeds exceeding the speed of sound, with ultrasonic taking the earlier meaning.
• Part of Speech: adjective (also used attributively); occasionally noun
• Word Family: supersonic (adj/n), supersonically (adv), supersonics (n), supersound (n, rare)
• Usage: India's induction of supersonic cruise missiles such as the BrahMos has materially sharpened its conventional deterrence, compressing an adversary's reaction window and recalibrating the strategic balance along contested frontiers.
• Synonyms: faster-than-sound, transonic, hypersonic, ultra-fast, high-velocity
• Antonyms: subsonic, slow, sluggish
• Mnemonic: Break it as SUPER + SONIC: "super" (above/beyond) the "sonic" (sound) barrier — go beyond the speed of sound, like a fighter jet bursting past Mach 1.

Stealth

• Pronunciation: /stɛlθ/
• Definition: In military technology, the design philosophy and suite of techniques used to make aircraft, missiles, ships, or vehicles less detectable by radar, infrared sensors, and other surveillance systems.
• Root: Old English stǣlþ = theft, secret action; stelan = to steal; -th = abstract noun suffix
• Origin: From Middle English stelthe ("theft, secret action"), from Old English stǣlþ, related to stelan ("to steal"); the military-technology sense emerged in the 1980s as radar-evading aircraft design advanced.

• Part of Speech: noun; also attributive/adjective (as in "stealth aircraft", "stealth taxation")
• Word Family: stealthy (adj), stealthily (adv), stealthiness (n), stealthy (adj), stealth (n/attrib adj)
• Usage: Critics argue that financing welfare schemes through fiscal drag and unindexed slabs amounts to taxation by stealth, eroding parliamentary accountability since the burden rises without any explicit vote in the legislature.
• Synonyms: secrecy, surreptitiousness, furtiveness, covertness, clandestineness, stealthiness
• Antonyms: openness, transparency, candour, overtness
• Mnemonic: Hidden inside "stealth" is "steal" plus -th: to steal something requires moving in secret, undetected — stealth is the manner of the silent thief.

Key Terms

Hypersonic Missiles

• Definition: Hypersonic missiles are weapons that travel at speeds exceeding Mach 5 (five times the speed of sound) while manoeuvring within the atmosphere, combining extreme velocity with in-flight steerability that makes them far harder to track and intercept than conventional ballistic or cruise missiles.
• Context: Unlike traditional ballistic missiles that follow a predictable parabolic path, hypersonic weapons use aerodynamic lift to manoeuvre during flight, collapsing an adversary's warning and response time. They fall into two broad classes: hypersonic glide vehicles (HGVs), boosted by a rocket and then gliding unpowered to target, and hypersonic cruise missiles (HCMs), powered throughout by air-breathing scramjet engines. Russia, China and the United States have led development, and India joined the select group of nations with this capability after a successful long-range test in November 2024.
• UPSC Relevance: Hypersonic missiles are a recurring theme in GS3 (defence technology, indigenisation, science and technology developments) and feature in Prelims via current-affairs items such as DRDO test launches and the BrahMos-II programme. This is a foundational concept underpinning questions on missile technology, defence self-reliance (Atmanirbhar Bharat), and strategic deterrence; aspirants should be able to distinguish HGVs from HCMs and explain why these weapons defeat conventional missile defences. There is no direct PYQ for this exact term, but it connects closely to the broader topic family of indigenous defence R&D and emerging strategic technologies.

BrahMos Missile

• Pronunciation: /ˈbrɑː.moːs ˈmɪs.aɪl/
• Definition: A supersonic cruise missile developed as a joint venture between India's DRDO and Russia's NPO Mashinostroyeniya (now NPO Mash), capable of being launched from land, sea, air (Su-30MKI), and submarine platforms at speeds of Mach 2.8 to 3.5 in a steep dive, with a range extended to up to 650 km (original: 290 km, extended after India joined the Missile Technology Control Regime/MTCR in 2016). It is the world's fastest supersonic cruise missile currently in operational service, featuring a two-stage propulsion system (solid booster + liquid ramjet sustainer) and a fire-and-forget capability with terminal manoeuvrability that makes it extremely difficult to intercept.
• Context: Named as a portmanteau of the Brahmaputra River (India) and the Moskva River (Russia), symbolising the bilateral partnership. BrahMos Aerospace Pvt. Ltd. was established on 12 February 1998 as a joint venture (India holds 50.5%, Russia 49.5%), with the missile first flight-tested on 12 June 2001. Key milestones: first air-launch from Su-30MKI (November 2017), first export contract to the Philippines ($375 million, January 2022). BrahMos-II, a hypersonic variant targeting Mach 7+ speed, is under development. The BrahMos Extended Range version (650 km) became possible after India's accession to MTCR in June 2016, which removed the 300 km range cap.
• UPSC Relevance: GS3 (Science & Technology / Defence). Prelims tests BrahMos specifications -- supersonic speed (Mach 2.8-3.5), range (up to 650 km), multi-platform capability (land, sea, air, submarine), India-Russia joint venture (BrahMos Aerospace, 1998), and distinction between cruise missiles (sustained propulsion, fly low to evade radar) and ballistic missiles (unpowered arc after initial boost). Mains asks about defence indigenisation under Atmanirbhar Bharat, BrahMos export to the Philippines (India's largest defence export deal), and India's missile technology capabilities in the context of strategic deterrence and MTCR membership (2016).

DRDO

• Pronunciation: /diː.ɑːr.diː.əʊ/
• Definition: The Defence Research and Development Organisation, India's premier military research and development agency under the Ministry of Defence, responsible for designing and developing defence systems and technologies for the Indian Armed Forces through a network of 41 laboratories and 5 DRDO Young Scientist Laboratories (DYSLs). Its mandate covers aeronautics, armaments, electronics, combat vehicles, missiles, naval systems, materials, CBRN defence, and life sciences.
• Context: Formed in 1958 by amalgamating the Technical Development Establishments (TDEs) of the Indian Army and the Directorate of Technical Development and Production (DTDP) with the Defence Science Organisation (DSO). Headquartered at DRDO Bhawan, Rajaji Marg, New Delhi. Key landmark projects: Integrated Guided Missile Development Programme (IGMDP, 1983, under Dr. A.P.J. Abdul Kalam -- developed Prithvi, Agni, Trishul, Akash, NAG; declared complete in 2008), LCA Tejas (4.5-generation fighter, inducted 2016), Arjun MBT (third-generation tank), INS Arihant nuclear reactor (powers India's nuclear submarine fleet), and Mission Shakti (anti-satellite test, 27 March 2019 -- India destroyed a live LEO satellite at 283 km altitude, becoming the fourth country with ASAT capability after US, Russia, and China). Defence exports have grown from Rs 1,521 crore (FY 2017) to over Rs 21,000 crore (FY 2024).
• UPSC Relevance: GS3 (Science & Technology / Defence). Prelims tests DRDO's founding year (1958), parent ministry (Defence, not Science & Technology), key products (Agni missiles, Tejas LCA, Arjun MBT, Kaveri engine, BrahMos -- note BrahMos is a joint venture, not solely DRDO), IGMDP (1983, Dr. Kalam, five missiles), and Mission Shakti (ASAT test, March 2019). Mains asks about defence indigenisation under Atmanirbhar Bharat (positive import lists, SRIJAN portal, iDEX for startups), DRDO's role in self-reliance vs criticism of delays and cost overruns, defence export growth, and the balance between indigenous R&D and technology imports (e.g., Rafale vs Tejas debate).

Sources

• DRDO Official Website
• Press Information Bureau — Ministry of Defence releases
• Ministry of Defence — Defence Acquisition Procedure
• BrahMos Aerospace Official Website
• PRS Legislative Research
• M. Laxmikanth, Indian Polity (7th Edition) — for Nuclear Command Authority structure
• Rajesh Singh, Indian Economy — for defence budget and indigenisation context