It is a little known fact that most major wars were not primarily won by the well known land battles or even by air power, but by effective Naval Blockades.
The ability to strangle an enemy state's economy by cutting off seaborne trade is considered by many, including the great naval theorist, Alfred Thayer Mahan, to be the raison d'être of having a Navy.
Indeed in his greatest work, The Influence of Sea Power Upon History, 1660-1783, published in 1890, he spends a great deal of time examining how the British acheived victory over the Dutch & French, and thus global empire, via Naval Power and especially the use of the Effective Blockade.
Major Blockades for the past 2 Centuries
Moving to more modern times, blockades were crucial in winning some of the largest and most consequential wars of the past 2 centuries.
World War One (1914 - 1919)
Many historians consider that the British Navy's "Distant Blockade" of Germany from Scapa Flow in Scotland to Norway, a distance of around 270 Nautical Miles, was the most important component of ultimate Allied Victory in World War One.
Spanish American War (1898)
The US Navy's blockade of the Spanish in Cuba in 1898 was a decisive military success that crippled Spanish operations and forced their surrender.
Further details of this blockade, in which Alfred Thayer Mahan served, can be found here:
American Civil War (1861 - 1865)
Other historians point to the critical impact of the Union's naval blockade of the Confederacy in the American Civil War.
In Part 7 of his magisterial History of Naval Warfare, Big Serge outlines in detail how the North's blockade of the South allowed it to leverage its industrial and naval superiority.
Other historians have also highlighted the importance of the Anaconda Plan blockade to the North's ultimate victory. https://www.nellaware.com/blog/anaconda-plan.html
Source: Library of Congress Geography and Map Division Washington, D.C. (Digital File Number: g3701s cw0011000)
Trump the Blockade Master
In many ways President Donald J Trump has returned American foreign policy to its pre-Wilsonian roots. President Woodrow Wilson was the first globalist US President and President Trump is rejecting his legacy and returning America to its patriotic, America First, Constitutionalist roots.
Late last year I highlighted what I called "The Trump Corollary to the Monroe Doctrine" in this post.
This is now being popularly called "The Donroe Doctrine" and with it Trump & the Department of War have re-established the Effective Naval Blockade as a key tool in geopolitics.
Naval Blockades played a major role in the the US Operation Southern Spear against Venezuela commencing in August 2025.
The US has also been enforcing an oil embargo against Cuba. This and the Venezuelan blockade has brought Cuba to a state of collapse and forced it to enter negotiations with the US. Cuba has very little electricity and is in a terrible economic state, especially after US operations in Venezuela cut off their last oil supplier.
Iran War (2026)
Unlike Venezuela, where blockade preceded military action, with Iran major kinetic strikes came first and blockade has followed. This is one of the reasons the complete destruction of the Iranian Navy was a key objective of Operation Epic Fury.
It is notable that the blockade line against Iran is substantially shorter (186 nautical miles) than the effective British blockade in WWI (270 Nm).
In this age of persistent surveillance from drones, satellites, helicopters, manned aircraft and ships the idea that any 100m long commercial vessel travelling as a maximum of 17 knots could successfully run the blockade is ludicrous.
In addition to the almost complete destruction of the Iranian military and military industrial base, Operation Epic Fury targeted IRGC linked economic targets as a prelude to the current blockade.
Here is a useful summary of the economic impact of the war on Iran.
▪️Pre-war, Iran earned ~$45.7B from oil annually (debatable number but we can start with this). But oil & gas together account for 65–75% of Iran's total export revenue and roughly 25% of its GDP. Lose oil and the blockade also cuts petrochemicals ($13–17B/yr, 85% of capacity now offline) and all other Gulf-routed exports. We're not talking about a 10% GDP hit alone here but a simultaneous wipeout of the entire hard currency earnings base.
▪️70% of steel production capacity destroyed. 85% of petrochemical export capacity offline, representing $30B in cumulative investment at Mahshahr alone, near-total write-off. This isn't a revenue shortfall. It's deindustrialization at a pace not seen since WWII. Total direct damage: $122–208B, or 38–48% of pre-war GDP, in 45 days.
▪️For 47 years, the regime refused to make any strategic investments in the welfare of Iranians. 58% of Iran's basic goods imports move through one single port; Bandar Imam Khomeini port, which requires Hormuz access. Iran imports 56%+ of its corn. The same chokepoint Iran closed to pressure others is the one its food supply depends on.
▪️The IRGC funds itself through barrels of oil that it gets to sell in the blackmarket. Kharg Island crude revenue, approximately $78B/year gross, is the IRGC's primary financial engine. National Iranian Oil Company keeps only 14.5% of export revenues; roughly a third goes to IRGC transfers. The blockade is strangling the security apparatus's ability to pay its own forces. When enforcers stop getting paid, loyalty math changes fast.
▪️Iran entered this conflict with a collapsing currency, insolvent banks, destroyed industry, no food import alternatives, and a fiscal budget that assumed oil revenues that the blockade has now zeroed out. "10% of GDP" is the ceiling on what Iran loses from oil alone. The floor of total damage is already 38% of GDP, and the clock is still running.
Source: Miad Maleki on X
Why Blockades are so effective
Blockades are a relatively low cost way to destroy the enemy's economy and thus their ability to make war. It has been true throughout history that soldiers have to be paid and if they are not, they will not fight.
Most major wars have been determined by economics, as much as military results.
There is also another, psychological aspect. Blockades create insidious, constant pressure that is difficult to fight back against. While Iran took a 1000:1 beating in the kinetic aspects of the war, at least they could feel they were fighting back, even if quite ineffectively and against mostly civilian targets.
But they are powerless against the blockade. They have no navy, so cannot fight it.
It constantly drains them and they become weaker and weaker, with little effort on the part of the USA. Turning around commercial ships is not difficult or particularly dangerous work, especially compared the the alternative of special forces raids on defended locations.
It also forces very difficult decisions on Iran.
Within a few days, oil storage on Kharg Island will be full and Iran will have to shut down fragile oil wells. This is a very difficult and painful decision for whatever is left of Iran's leadership.
With money running out, Iran will have to stop paying more and more of their IRCG thugs. Who gets cut is a very difficult decision.
These painful decisions and Iran passing through the stages of grief (they are currently in denial & rage) will bring Iran to agree to US demands.
It is only a matter of time.
As Trump says, there is no rush.
Most blockades lasted many months if not years.
This blockade is very new.