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U.S. military says hit Iran missile sites near Strait of Hormuz with 'bunker buster' bombs

March 18, 2026 6 min read International Relations Internal Security GS2 (International Relations Security) GS3 (Internal Security)
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What Happened

  • On March 18, 2026, US military forces struck hardened Iranian anti-ship missile sites along Iran's coastline near the Strait of Hormuz using GBU-72 Advanced 5K Penetrator bunker-buster bombs — 5,000-pound (approximately 2,270 kg) precision-guided munitions.
  • The strikes were the first major US military action targeting missile positions directly threatening commercial navigation in the Strait of Hormuz, which Iran had partially closed following the start of the US-Israel war on Iran (February 28, 2026).
  • The GBU-72, first deployed in 2021, was developed specifically to destroy hardened, deeply buried targets and is deployed from F-15E Strike Eagles and B-2 Spirit bombers.
  • Iran's anti-ship cruise missiles at these sites had posed an ongoing threat to the approximately 20 million barrels per day of oil that transits through Hormuz.
  • The US has separately used 30,000-pound (13,600 kg) bombs in strikes against Iranian nuclear sites; the 5,000-pound GBU-72 represents a more targeted application against coastal missile batteries.
  • Iran has declared Hormuz closed to US, Israeli, and Western-allied vessels, while allowing passage to some Indian-flagged and Saudi oil tankers.

Static Topic Bridges

The Strait of Hormuz is an international strait under the United Nations Convention on the Law of the Sea (UNCLOS, 1982), which guarantees the right of "transit passage" — a right that cannot be suspended even by the coastal state. This legal framework is at the heart of the dispute between Iran's closure declaration and US/international insistence on free navigation.

  • UNCLOS Part III (Articles 34-45) governs international straits. Article 38 establishes the right of "transit passage" — the continuous and expeditious passage through a strait used for international navigation.
  • Unlike "innocent passage" (which can be temporarily suspended by coastal states in territorial seas), transit passage through international straits cannot be suspended.
  • The Strait of Hormuz is approximately 55–95 km wide; Iran and Oman are the two coastal states. The entire strait lies within their territorial waters, but UNCLOS preserves the right of transit passage regardless.
  • Iran is a signatory to UNCLOS (ratified 1982) but has frequently claimed the right to restrict passage during armed conflict under customary international law.
  • The US, ironically, is not a formal party to UNCLOS (Senate never ratified it) but invokes its navigational freedom provisions as customary international law.

Connection to this news: The US strikes on Iranian missile sites are framed as enforcing freedom of navigation — the practical military expression of the legal right of transit passage. UPSC GS2 frequently tests the legal framework of maritime zones and international straits.

Precision-Guided Munitions (PGMs) and Modern Warfare

Precision-Guided Munitions (PGMs) — also called "smart bombs" — are weapons that use guidance systems (GPS, laser, inertial navigation) to strike specific targets with high accuracy, minimising collateral damage relative to unguided munitions. The GBU-72 is the latest in a line of American deep-penetrating PGMs designed to defeat hardened and deeply buried targets (HDBTs).

  • GBU-72 Advanced 5K Penetrator: 5,000 lb (2,270 kg) class; uses JDAM (Joint Direct Attack Munition) GPS/INS tail guidance kit; designed for deployment from F-15E Strike Eagle and B-2 Spirit bomber.
  • GBU-28 "Bunker Buster": 5,000 lb, used in Gulf War I (1991) — first dedicated deep-penetrating bomb; penetrates up to 6 metres of reinforced concrete or 30 metres of earth.
  • GBU-57 Massive Ordnance Penetrator (MOP): 30,000 lb (13,600 kg) — the largest non-nuclear bomb in the US arsenal; deployed by B-2 bombers and used against Iranian nuclear sites in the current conflict.
  • The ability to destroy hardened, deeply buried facilities (like underground missile batteries and nuclear enrichment sites) has become a critical military capability as adversaries increasingly put strategic assets underground.
  • India's interest in PGMs: India has acquired JDAM guidance kits for its own munitions and operates the BrahMos supersonic cruise missile — the world's fastest operational cruise missile, developed jointly with Russia.

Connection to this news: The choice of the GBU-72 (rather than the GBU-57 MOP used against nuclear sites) for coastal missile battery strikes signals a calibrated escalation — destructive enough to neutralise the threat but not maximally escalatory. This distinction is important for understanding US escalation management, a theme UPSC GS2 Mains tests in questions on US foreign policy.

Iran's Anti-Access/Area Denial (A2/AD) Strategy

Anti-Access/Area Denial (A2/AD) is a military strategy that uses a combination of long-range missiles, naval mines, submarines, and fast-attack boats to deny an adversary's ability to enter and operate within a defined geographic area. Iran has developed one of the most sophisticated A2/AD strategies in the region, centred on the Strait of Hormuz.

  • Iran's A2/AD arsenal includes: C-802 and Noor anti-ship cruise missiles, Khalij Fars ballistic anti-ship missiles (specifically designed to target aircraft carriers), submarines (Kilo-class and domestically produced Fateh-class), IRGC Naval fast-attack swarm boats, and extensive coastal artillery.
  • The IRGC Navy (separate from the regular Iranian Navy) controls the Strait of Hormuz and has historically engaged in "tanker wars" — notably during 1984-88 and again in 2019.
  • Iran's strategy relies on asymmetric warfare: using cheap, numerous, fast systems to impose costs on a technologically superior adversary rather than engaging in conventional naval battle.
  • The Strait's narrowness (2-mile shipping lanes) makes A2/AD particularly effective — missiles and mines can cover the entire navigable width.
  • The US counterpart strategy is called AirSea Battle (now Multi-Domain Operations), combining air and naval strikes to degrade A2/AD capabilities before they can be fully employed.

Connection to this news: The US strikes on Iranian anti-ship missile sites are a direct application of the AirSea Battle concept — degrading Iran's A2/AD capability to restore freedom of navigation. For UPSC, this illustrates how geographic chokepoints translate into military strategy.

International Law on Use of Force and Self-Defence

The United Nations Charter (1945) prohibits the use of force in international relations (Article 2(4)) with two exceptions: Security Council authorisation (Chapter VII) and individual or collective self-defence (Article 51). The US has invoked Article 51 to justify military operations in the current conflict.

  • Article 2(4) UN Charter: "All Members shall refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any state."
  • Article 51: Preserves "the inherent right of individual or collective self-defence if an armed attack occurs against a Member of the United Nations."
  • Chapter VII: Allows the Security Council to authorise force to maintain/restore international peace and security — requires no veto from P5 members.
  • The customary right of "protection of nationals abroad" is sometimes invoked to justify strikes on missile systems threatening one's citizens and military personnel.
  • The Hague Conventions and Geneva Conventions govern the conduct of warfare (jus in bello), even when the decision to go to war (jus ad bellum) is contested.

Connection to this news: The legality of US strikes on Iranian territory is a contested international law question — the US argues self-defence and freedom of navigation enforcement; Iran and several other states argue it constitutes unlawful aggression. This is a model UPSC GS2 question scenario.

Key Facts & Data

  • GBU-72 Advanced 5K Penetrator: 5,000 lb (2,270 kg), GPS/INS guided, deployed from F-15E and B-2
  • GBU-57 MOP: 30,000 lb (13,600 kg) — used against Iranian nuclear sites, the largest conventional bomb in US arsenal
  • Strait of Hormuz: ~20 million barrels/day oil transit (2025); 34% of global crude oil trade
  • War start date: February 28, 2026 — US-Israel joint strikes on Iran
  • UNCLOS Article 38: right of transit passage through international straits — cannot be suspended
  • Iran ratified UNCLOS in 1982; USA has not ratified but treats navigational provisions as customary international law
  • UN Charter Article 2(4): prohibition on use of force; Article 51: right of self-defence
  • BrahMos cruise missile: India-Russia joint venture, world's fastest operational cruise missile (~Mach 2.8)