The Strait of Hormuz, a narrow waterway once carrying roughly a fifth of the world’s oil and gas, remains effectively closed after the United States and Iran imposed competing blockades.

Naval blockades are one of the oldest weapons in warfare, requiring no ground troops or invasion, just the ability to cut off what an enemy needs to survive. These blockades have reshaped economies, societies and alliances across generations, sometimes with instant shockwaves, sometimes with effects only seen later.

From Israel’s ongoing siege of the Gaza Strip to blockades during World War I, here are some notable naval blockades in modern history:

Israel’s siege of Gaza (2007-present)

Israel’s complete land, sea and air blockade of the Gaza Strip is one of the longest sieges in modern history.

Launched in 2007, Israel has limited the entry of goods and essential supplies, causing a prolonged humanitarian and economic crisis for the Strip’s 2.3 million people, who cannot travel freely.

Before Israel’s genocidal war on Gaza began in October 2023, fishermen were restricted to 6-15 nautical miles (11-28km) from shore, well below the 20-nautical-mile (37km) zone guaranteed by the Oslo Accords.

After 2023, with Israel’s policy of starving the population, fishermen have taken extreme measures to feed their families, leading to many being killed by Israeli fire.

Since 2008, several Freedom Flotilla vessels have attempted to break the Israeli blockade. Since 2010, all flotillas attempting to break the Gaza blockade have been intercepted or attacked by Israel in international waters.

On April 30, Israel raided 22 out of the 58 vessels in the most recent Global Sumud Flotilla campaign in international waters more than 1,000km (620 miles) from Gaza.

Blockade of Biafra (1967-70)

During the Nigerian Civil War, which began in July 1967, the Nigerian federal government imposed a land, sea and air blockade on the secessionist Republic of Biafra shortly after it declared independence.

The blockade led to widespread starvation, widely seen as a deliberate wartime strategy, transforming a territorial conflict into a global humanitarian crisis. Death tolls vary, but it is estimated that one to two million people died, the vast majority from hunger and disease rather than direct conflict.

The nearly three-year-long blockade ended with the Biafran surrender in January 1970.

Beira Patrol blockade (1966-75):

The Beira Patrol was a nine-year-long blockade by the British navy to prevent oil from reaching Rhodesia, present-day Zimbabwe, through the Mozambican port of Beira, enforced under United Nations sanctions following Rhodesia’s unilateral declaration of independence.

The blockade largely failed its strategic goal. Rhodesia continued receiving oil via South Africa and other Mozambican ports, which the UN resolution did not authorise the British navy to intercept.

Additionally, the cost to the United Kingdom was substantial. The operation tied up 76 naval ships over nine years, with two frigates required on station at all times.

The blockade ended in July 1975, when Mozambique’s newly gained independence from Portugal allowed it to credibly commit to blocking oil transit to Rhodesia, rendering the naval patrol redundant.

Cuban Missile Crisis ‘quarantine’ (1962)

In October 1962, the US ordered a naval “quarantine” of Cuba after US U-2 spy planes discovered Soviet nuclear missile sites under construction on the island.

The US deliberately called it a “quarantine” rather than a blockade, which would have been legally an act of war, aiming to prevent the Soviets from bringing in more military supplies and to pressure them to remove the missiles already there.

The quarantine drew a line 500 nautical miles (920km) from Cuba’s coast, with US warships authorised to stop, search, and turn back any vessel carrying offensive weapons if necessary.

The crisis brought the world to the brink of nuclear war. The then-Soviet First Secretary Nikita Khrushchev called the blockade “outright piracy” and an act of aggression, and initially ordered ships to proceed. For several days, Soviet vessels steamed towards the quarantine line as the world watched.

The most dangerous phase of the standoff lasted 13 days. An agreement was reached in which the Soviets would dismantle their offensive weapons in Cuba in exchange for a US public declaration not to invade Cuba, and a secret agreement to remove US Jupiter missiles from Turkiye.

The naval quarantine was formally ended on November 20, 1962, after all offensive missiles and bombers had been withdrawn.

Blockade of Wonsan (1951-53)

During the Korean War, UN naval forces led by the US imposed a blockade of the North Korean port of Wonsan in February 1951, lasting nearly two and a half years.

It aimed to deny the North Korean navy access to the city, which was strategically significant for its large harbour, airfield and petroleum refinery.

The blockade was preceded by a dangerous mine-clearance operation in October 1950. North Korean forces had been well supplied by the Soviet Union and China with sea mines, and during the clearance, the sweepers USS Pledge and USS Pirate were sunk, killing 12 men and wounding dozens.

The operation successfully constrained North Korean and Chinese forces on the east coast, forcing them to divert thousands of troops and artillery pieces away from the front line. UN forces also captured several harbour islands, which strengthened the blockade’s grip on the port.

The blockade ended after 861 days with the signing of the Korean Armistice Agreement in July 1953. By that point, allied naval fire had almost levelled Wonsan.

US submarine blockade of Japan (1942-45)

The US imposed a submarine blockade against Japan during the Pacific War.

The blockade began taking shape in 1942, combining US naval submarine attacks on merchant shipping with minelaying operations to cripple Japan’s war capabilities, disrupt shipping and cut off vital supplies such as food and fuel.

As an island nation, Japan was especially vulnerable, almost entirely dependent on imports of oil, rubber and raw materials. Its economy and military could not function without open sea lanes.

Over the course of the war, US submarines sank some 1,300 Japanese merchant ships and roughly 200 warships. By 1945, oil imports had effectively ceased.

Food imports collapsed, causing significant shortages and malnutrition across Japan by 1945, though the extent of civilian starvation is disputed.

After the US dropped atomic bombs on Hiroshima on August 6 and Nagasaki on August 9, 1945, Japan announced its surrender on August 15, bringing the blockade and the Pacific War to an end.

Blockade of eastern Mediterranean (1915-18)

In August 1915, during World War I, the Allied forces imposed a blockade of the eastern coast of the Mediterranean to cut off military supplies and weaken the Ottoman Empire’s war effort.

The declared area ran from the intersection of the Aegean Sea and the Mediterranean Sea in the north to the Egyptian frontier in the south. The blockade was initiated by Britain and France, later assisted by Italy and other Allied powers.

The consequences were devastating. Military supplies, munitions, oil, food and medicine were all targeted. The food crisis was compounded by a locust plague in 1915 and a severe drought, contributing to severe famine across Lebanon and Greater Syria.

Reports suggest the famine led to 500,000 deaths by 1918, mostly civilians, with Mount Lebanon losing an estimated one-third of its population. Mass migration followed.

The blockade remained in place throughout the war and lifted only when Allied forces occupied Beirut and Mount Lebanon in October 1918.

Allied blockade of Germany (1914-19)

The British navy began blockading Germany almost immediately after the outbreak of the war in August 1914.

The naval blockade extended from the English Channel to Norway, cutting off Germany from the oceans.

Britain mined international waters to prevent ships from entering the ocean, creating danger even for neutral vessels.

Germany responded by declaring the seas around the British Isles a “military area”, prompting Britain and France to ban all goods to and from Germany.

The blockade’s most devastating consequence was famine. The winter of 1916-17, known as the Turnip Winter, marked one of the harshest years in wartime Germany.

The blockade had cut off food and fertiliser imports, a failed potato harvest left little to fall back on, and a breakdown in food distribution compounded the crisis. It is estimated that between 424,000 and 763,000 civilians died from diseases related to hunger and malnutrition.

The blockade was not yet fully lifted until July 1919, after the Treaty of Versailles had been signed.