blocus

Blockade entered English from French blocus, which came from Dutch blokhuis, a compound of blok (block, log) and huis (house). A blokhuis was a wooden fort or blockhouse built to control a harbor or river crossing. The strategic leap from the building to the tactic happened in the sixteenth century: if you built blockhouses at the mouth of a harbor, you could control who entered. The building was the means. The blockade was the effect.

Naval blockades became a standard weapon of European warfare by the 1600s. The Dutch blockaded the Scheldt estuary, strangling Antwerp's trade. The British developed the close blockade into an art form during the Napoleonic Wars: from 1803 to 1805, the Royal Navy maintained a continuous blockade of French ports, keeping Napoleon's fleet bottled up. Admiral Cornwallis kept his squadron off Brest for months at a time. The sailors ate salt pork and watched a harbor they could not enter.

The word's most famous American use was the Union blockade of Confederate ports during the Civil War (1861–1865). The Anaconda Plan, as the press called it, aimed to strangle the Confederacy's trade. Over four years, the Union Navy grew from 42 ships to over 600, patrolling 3,500 miles of coastline. The blockade was imperfect — blockade runners slipped through — but it worked. The Confederacy could not export cotton or import weapons in sufficient quantities.

The Berlin Blockade of 1948–1949 was the last great use of the word in its pure military sense. The Soviets blocked all land access to West Berlin. The Western Allies responded with an airlift, flying supplies over the blockade for eleven months. The word acquired a Cold War charge: blockade was what the other side did. By the time of the Cuban Missile Crisis in 1962, President Kennedy avoided the word entirely, calling the naval cordon around Cuba a 'quarantine' because 'blockade' was legally an act of war.