Straits and chokepoints

Detail

Key terms

• A strait is a narrow strip of sea that joins two larger seas or oceans. It has land on both sides.
• A channel is also a sea passage between two land masses. It is usually wider than a strait. The Mozambique Channel is an example.
• A chokepoint is a narrow sea passage that a large share of world shipping must pass through. If it is blocked, ships must take long detours, freight and insurance costs rise, and fuel prices go up.
• In April 2026 the IMO (International Maritime Organization: the UN body for shipping) named six waterways that conflict can easily disrupt [6]:
• the Suez Canal
• the Bab-el-Mandeb Strait
• the Strait of Hormuz
• the Straits of Malacca and Singapore
• the Turkish Straits (Strait of Istanbul, Strait of Çanakkale and the Sea of Marmara)
• the Panama Canal

Master table

Strait	Joins	Between	Size
Strait of Hormuz	Persian Gulf – Gulf of Oman and Arabian Sea	Iran – Oman (Musandam)	—
Bab-el-Mandeb	Red Sea – Gulf of Aden	Yemen – Djibouti and Eritrea	about 30 km wide
Strait of Malacca	Andaman Sea – South China Sea	Malay Peninsula – Sumatra	about 800 km long
Mozambique Channel	arm of the Indian Ocean	Mozambique – Madagascar	about 400 km at its narrowest
Strait of Gibraltar	Atlantic – Mediterranean	Spain – Morocco	about 14 km wide
Bosphorus	Black Sea – Sea of Marmara	runs through Istanbul (Europe/Asia)	30 km long [11]
Kerch Strait	Sea of Azov – Black Sea	Russia's Taman Peninsula – Crimea	—
Taiwan Strait	East China Sea – South China Sea	Taiwan – mainland China	about 130-180 km wide
Bering Strait	Pacific – Arctic	Russia's Chukotka – Alaska	about 82 km wide
Drake Passage	Atlantic – Pacific	Cape Horn – Antarctic Peninsula	wide and rough

A. The Indian Ocean's gates: India's trade and energy lifelines

Strait of Hormuz

• Location: Iran lies to the north. Oman's Musandam peninsula, a piece of Oman cut off from the rest of the country by UAE territory, lies to the south.
• Joins: the Persian Gulf with the Gulf of Oman and the Arabian Sea.
• It is the only sea route out of the Persian Gulf. Iran, Iraq, Kuwait, Saudi Arabia and the UAE send most of their oil exports through it [7].
• Oil flow:
• About one-fifth of the world's oil passes through it, along with much LNG (liquefied natural gas).

• A recent estimate puts the flow at about 20.3 million barrels a day, roughly a quarter of the oil traded by sea (Britannica, mid-2020s) [7].

• India's stake: a large share of India's crude oil and LPG imports comes through Hormuz.

• Ranking: Hormuz and Malacca are the two busiest oil chokepoints [8].
• 2026 crisis (verify current):
• Late February 2026: the US and Israel bombed Iran, and shipping through Hormuz became unsafe.
• By April 2026, up to 20,000 seafarers on about 2,000 ships were stranded inside the Persian Gulf [6].

• The IMO Secretary-General said that "civilian seafarers are not combatants" [6].

• India's response, Operation Sankalp:

• The Indian Navy began this maritime security operation in the Gulf region on 19 June 2019.
• It was started to keep Indian-flagged ships safe as they passed through Hormuz [4].
• By mid-2022, 36 warships had been deployed under it. They escorted about 453 Indian-flagged merchant ships carrying about 361 lakh tonnes of cargo [4].

Bab-el-Mandeb ("Gate of Grief")

• Location: about 30 km wide, with Yemen (Arabian Peninsula) on one side and Djibouti and Eritrea (Horn of Africa) on the other.
• Joins: the Red Sea with the Gulf of Aden, and through it the Indian Ocean.
• Perim Island (Yemen) sits at the narrowest point. Every ship using the Red Sea and the Suez Canal must pass it [9].
• Importance:
• It is the third-busiest oil chokepoint, carrying about one-tenth of the oil traded by sea [8].

• About one-fourth of global container trade also passes through it [9].

• What the Houthi attacks did (from late 2023):

• Houthi forces in Yemen attacked merchant ships after the Israel-Hamas war began in 2023.
• Traffic through the strait fell below half of its normal level [8].
• Many ships went around the Cape of Good Hope instead. That is a much longer route.

• Freight costs went up for India's trade with Europe.

• The Indian Navy's response (verify current):

• From mid-December 2023, the Navy widened Operation Sankalp to cover the Red Sea, the Gulf of Aden and the Arabian Sea [2].
• First 100 days (14 December 2023 to 23 March 2024) [2]:
  • more than 110 lives saved, including 45 Indian seafarers
  • 15 lakh tonnes of fertiliser, crude oil and finished products escorted
  • nearly 1,000 boarding operations
  • more than 3,000 kg of narcotics seized
  • more than 450 merchant ships assured of the Navy's presence

• Over one year (2024) [3]:

  • more than 30 ships deployed
  • more than 25 incidents handled
  • more than 400 lives saved, whatever the crew's nationality

• Earlier role: the Indian Navy has run an anti-piracy patrol in the Gulf of Aden since 2008 [5].

Strait of Malacca

• Location: between the Malay Peninsula (Malaysia; Singapore at its southern tip) and Sumatra (Indonesia).
• Joins: the Andaman Sea, an arm of the Indian Ocean, with the South China Sea.
• Shape:
• about 800 km long and funnel-shaped
• only about 65 km wide in the south

• widens to about 249 km in the north [10]

• Importance:

• It is one of the busiest shipping lanes in the world.

• It is China's main oil route.

• "Malacca dilemma": this is China's fear that a blockade of this one strait could cut off most of its imported oil.

• India's position:
• The strait's western entrance lies close to India's Andaman and Nicobar Islands.

• The Six Degree Channel separates Great Nicobar (India) from Sumatra (Indonesia).

• Alternative routes: the Sunda Strait (Sumatra – Java) and the Lombok Strait (Bali – Lombok). Both take ships further south.

Mozambique Channel

• Location: an arm of the Indian Ocean between Mozambique (mainland Africa) and Madagascar. It is about 400 km wide at its narrowest.
• Role:
• It lies on the Cape route. Ships use this route between the Indian Ocean and the Atlantic when they avoid Suez and Bab-el-Mandeb.

• Its importance grows whenever the Red Sea is unsafe.

• Nearby:

• French islands (such as Mayotte)
• Mauritius's Agalega islands, where India has developed facilities (see Section 10)

B. Europe's gates

Strait of Gibraltar

• Location: about 14 km wide at its narrowest, between Spain (Europe) and Morocco (Africa).
• It is the only natural link between the Atlantic Ocean and the Mediterranean Sea.
• Territories on its shores:
• British Gibraltar on the north shore

• Spanish Ceuta on the African south shore

• Two-layer water exchange:

• Cause: the Mediterranean loses more water to evaporation than it gets from rain and rivers.
• Process: this makes its water saltier and heavier (denser).
• Result: lighter, less salty Atlantic water flows in at the surface. Heavy, salty Mediterranean water flows out at depth. (See ocean-relief-temperature-salinity.)

The Turkish Straits

This is one sea route made of three parts. From north to south:

1. Bosphorus (Strait of Istanbul) - It runs through Istanbul and joins the Black Sea with the Sea of Marmara. - It forms part of the border between Europe and Asia. - It is about 30 km long, at most 3.7 km wide, and only 750 m wide at its narrowest [11].

2. Sea of Marmara: a small inland sea that links the two straits.

3. Dardanelles (Strait of Çanakkale) - It joins the Sea of Marmara with the Aegean Sea, a part of the Mediterranean. - The Gallipoli peninsula lies on its European side.

Montreux Convention (20 July 1936) [12]:

• What it did:
• gave Turkey back its full right to fortify the straits (build military defences along them)

• limited the navies of countries outside the Black Sea

• Wartime power: Turkey can block warships from passing.

• 2022 use: after Russia invaded Ukraine in 2022, Turkey closed the straits to the warships of the countries at war.

Kerch Strait

• Location: between Russia's Taman Peninsula and Crimea.
• Joins: the Sea of Azov with the Black Sea.
• Russia's Crimean Bridge (2018) crosses it.

Other European straits

Strait	Location and role
Strait of Dover	narrowest part of the English Channel (England – France); Channel Tunnel (1994) runs under the sea here
Oresund and the Danish straits	Denmark – Sweden; the Baltic Sea's only way out to the North Sea
Strait of Otranto	Italy – Albania; joins the Adriatic and Ionian Seas
Strait of Messina	mainland Italy – Sicily

C. Pacific and polar gates

Taiwan Strait

• Location: about 130-180 km wide, between Taiwan and mainland China.
• Joins: the East China Sea with the South China Sea.
• It is a major shipping lane and a military flashpoint, because China claims Taiwan.

Bering Strait

• Location: about 82 km wide, between Russia's Chukotka (Asia) and Alaska (USA, North America).
• Joins: the Pacific Ocean with the Arctic Ocean.
• International Date Line:
• This is the imaginary line, roughly along 180° longitude, where the calendar date changes by one day.
• It runs between the two Diomede islands. Big Diomede belongs to Russia and Little Diomede to the USA.
• The two islands are only a few kilometres apart, yet their calendars are one day apart.

Drake Passage

• Location: the wide, rough stretch of sea between Cape Horn (the southern tip of South America) and the Antarctic Peninsula.
• Joins: the Atlantic and Pacific Oceans.
• Antarctic Circumpolar Current (ACC):
• What it is: the ACC is the strong current that flows from west to east right around Antarctica.
• Why it squeezes through here: no land blocks it anywhere along its path, and the Drake Passage is the narrowest gap it has to pass through.

• Result: very rough seas. (See ocean-movements.)

• Sheltered alternative: the Strait of Magellan, which cuts through the southern tip of mainland South America.

Other straits to locate on the map

Strait	Between	Joins / note
Korea (Tsushima) Strait	South Korea – Japan	Sea of Japan – East China Sea
La Perouse Strait	Sakhalin (Russia) – Hokkaido (Japan)	Sea of Japan – Sea of Okhotsk
Tsugaru Strait	Honshu – Hokkaido (Japan)	Sea of Japan – Pacific
Torres Strait	Australia – New Guinea	Arafura Sea – Coral Sea
Bass Strait	mainland Australia – Tasmania	—
Cook Strait	North Island – South Island (New Zealand)	—
Davis Strait	Greenland – Baffin Island (Canada)	Baffin Bay – Labrador Sea
Denmark Strait	Greenland – Iceland	Arctic – North Atlantic
Florida Strait	Florida (USA) – Cuba	Gulf of Mexico – Atlantic
Yucatan Channel	Mexico (Yucatan) – Cuba	Gulf of Mexico – Caribbean Sea

• Covered in other notes:
• Canals (Suez 1869, Panama 1914, Kiel) and sea routes: world-transport-communication.
• The Palk Strait and the Ten Degree and Nine Degree Channels: india-neighbours and india-location.

Prelims Hooks

• Strait – the two countries on its sides:
• Hormuz: Iran – Oman (Musandam)
• Bab-el-Mandeb: Yemen – Djibouti and Eritrea
• Malacca: Malaysia – Indonesia (Sumatra)
• Gibraltar: Spain – Morocco
• Bering: Russia – USA

• Torres: Australia – Papua New Guinea

• Ranking of oil chokepoints: Hormuz and Malacca are the busiest; Bab-el-Mandeb is third (about one-tenth of oil traded by sea) [8].

• Turkish Straits, north to south: Black Sea → Bosphorus → Sea of Marmara → Dardanelles → Aegean Sea. The Montreux Convention dates from 1936 [12].
• Kerch Strait joins the Sea of Azov (not the Caspian Sea) with the Black Sea. The Crimean Bridge was built in 2018.
• Trap: the Mozambique Channel is part of the Indian Ocean, not the Atlantic.
• Trap: the Drake Passage lies between Cape Horn and the Antarctic Peninsula, not the Cape of Good Hope. The Strait of Magellan is the sheltered route north of it.
• The International Date Line passes between Big Diomede (Russia) and Little Diomede (USA) in the Bering Strait.
• At Gibraltar, Atlantic water flows in at the surface and salty Mediterranean water flows out at depth.
• Operation Sankalp began on 19 June 2019 to protect Indian-flagged ships passing Hormuz [4]. The Gulf of Aden anti-piracy patrol has run since 2008 [5].
• Malacca is funnel-shaped: about 65 km wide in the south and about 249 km in the north [10].

Mains Points

• Energy security (GS-III):
• A large share of India's crude oil and LPG comes through Hormuz.
• The 2026 crisis stranded up to 20,000 seafarers on about 2,000 ships [6].
• This shows how one strait can halt supply.

• India's responses:

  • strategic petroleum reserves
  • buying oil from more countries
  • naval escort under Operation Sankalp [2][4]

• Trade costs and rerouting:

• The Houthi attacks cut Red Sea traffic to below half its normal level [8].
• Ships went the long way, around the Cape of Good Hope.
• Voyages, freight costs and insurance costs all went up.

• Indian exporters to Europe were hit, and the Mozambique Channel and Cape route became more important.

• India's geostrategic advantage (GS-I/GS-III):

• The Andaman and Nicobar Islands sit beside the Malacca entry and the Six Degree Channel. China fears this, as its "Malacca dilemma" shows.
• India also has links to Agalega and the western Indian Ocean.

• These positions let India act as a net security provider (a country that keeps the sea safe for others, not only for itself). The Navy saved more than 400 lives in 2024 [3].

• Physical geography explains political rules:

• Narrow width: Turkey can control the 750 m Bosphorus under the 1936 Montreux Convention [11][12].
• Saltier water: the Mediterranean's high salinity drives the two-layer flow at Gibraltar.
• Open sea around Antarctica: with no land in the way, the ACC is forced through the Drake Passage.