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U.S. military says it will start blockade of all ships going to and from Iran on Monday

April 12, 2026 4 min read International Relations Internal Security GS Paper 2 (IR) GS Paper 3 (Energy Security)
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What Happened

  • US Central Command (CENTCOM) announced that from April 13, 2026, US forces would begin a naval blockade preventing all ships from entering or departing Iranian ports and coastal areas on the Arabian Gulf and Gulf of Oman.
  • The blockade was declared "impartial" — to be enforced against vessels of all nations, though CENTCOM stated it would not impede freedom of navigation for ships transiting the Strait of Hormuz to and from non-Iranian ports.
  • The announcement came after US-Iran peace talks in Islamabad collapsed without a ceasefire agreement, following 21 hours of failed negotiations.
  • Two US Navy guided-missile destroyers transited the Strait of Hormuz — the first such passage since the start of the Iran conflict six weeks prior — signalling active naval positioning.
  • Mine-clearing operations in the Strait were already underway ahead of the formal blockade.

Static Topic Bridges

A naval blockade is a military operation to prevent passage of vessels to or from an enemy's coastline or ports. Under the laws of naval warfare codified in the San Remo Manual (1994) on International Law Applicable to Armed Conflicts at Sea, a blockade is legally permissible during armed conflict, but must be declared formally, must not bar access to neutral ports, must be effective, and must not cause disproportionate harm to civilian populations.

  • The San Remo Manual (1994) is the key contemporary reference on the law of naval warfare; it codifies conditions for a lawful blockade.
  • A blockade that cuts off humanitarian supplies can be challenged as a violation of international humanitarian law.
  • The US is not a party to UNCLOS (United Nations Convention on the Law of the Sea, 1982), but recognises most of its provisions as customary international law.
  • UNCLOS Article 37–44 govern "transit passage" through international straits — a right that cannot be suspended even during armed conflict.

Connection to this news: The US blockade targets Iranian ports specifically, while preserving transit passage through the Strait of Hormuz for non-Iranian vessels — a calibration designed to maintain legal legitimacy under international law while applying maximum economic pressure on Iran.

Strait of Hormuz: A Critical Global Chokepoint

The Strait of Hormuz is a narrow waterway between Iran and Oman, connecting the Persian Gulf to the Gulf of Oman and the Arabian Sea. It is approximately 33 km wide at its narrowest point. Roughly 20–21 million barrels of oil per day — about 20% of global petroleum trade — pass through this strait, making it the world's most strategically important maritime chokepoint.

  • About 20% of global oil trade and 20% of global LNG trade passes through the Strait of Hormuz.
  • Iran has previously threatened to close the strait in response to sanctions (2012, 2018–19).
  • India imports over 60% of its crude from the Persian Gulf, with a significant portion transiting Hormuz.
  • The Strait lies between Iran (north) and Oman and the UAE (south); neither Iran nor the US is a party to UNCLOS.
  • India monitors 20+ Indian-flagged ships with 540+ seafarers operating near the Strait amid the 2026 crisis.

Connection to this news: The US blockade of Iranian ports (distinct from closing the Strait entirely) creates a precedent for naval coercion in one of the world's most sensitive chokepoints, with direct implications for India's energy supply chains.

US Central Command (CENTCOM)

CENTCOM is one of the 11 Unified Combatant Commands of the US Armed Forces, responsible for military operations in the Middle East, Central Asia, and South Asia region (20 countries). It was established in 1983, replacing the Rapid Deployment Joint Task Force, and is headquartered in Tampa, Florida.

  • CENTCOM's Area of Responsibility (AOR) covers 20 countries from Egypt to Pakistan, including the Persian Gulf region.
  • CENTCOM has historically coordinated Operation Earnest Will (1987–88) — US escort of Kuwaiti tankers through Hormuz during the Iran-Iraq War "Tanker War."
  • The 1987 reflagging operation is a historical precedent for US naval intervention to keep Hormuz open.
  • CENTCOM coordinates with the Combined Maritime Forces (CMF), a 38-nation naval partnership based in Bahrain.

Connection to this news: CENTCOM's formal blockade announcement represents a significant escalation — converting what was a wartime air campaign against Iran into a sustained naval siege, with potential long-term consequences for global energy markets and India's supply security.

Key Facts & Data

  • US blockade effective date: April 13, 2026, 10 AM ET
  • Strait of Hormuz width at narrowest: approximately 33 km
  • Global oil trade transiting Hormuz: ~20% (~20–21 million barrels/day)
  • India's crude import dependence on Persian Gulf: over 60%
  • India monitors 20 Indian-flagged ships with 540+ seafarers in the Persian Gulf
  • Indian Navy deployed warships near Persian Gulf to safeguard merchant shipping
  • CENTCOM established: 1983, headquartered Tampa, Florida
  • San Remo Manual on Naval Warfare: 1994