What was the name of the Union's strategy to blockade Confederate ports?

The Union’s strategy to blockade Confederate ports was called the Anaconda Plan.

Union General-in-Chief Winfield Scott proposed the plan in 1861. Its central idea was to surround the Confederacy with a naval blockade, cutting off overseas trade and preventing the export of cotton or the import of weapons, ammunition, and other supplies. A second major element called for Union forces to seize the Mississippi River, splitting the Confederacy in two.

The name came from the image of a giant anaconda slowly squeezing its prey. Critics mocked Scott’s proposal as too slow and passive, preferring aggressive campaigns against Confederate armies and Richmond. In practice, the Union blockade required military action to capture coastal bases and ports, so it was more complicated than a simple line of ships offshore.

The plan was not the sole cause of Confederate defeat, but the blockade weakened the Southern economy, disrupted trade, and made it increasingly difficult to supply Confederate forces. Lincoln separately proclaimed a blockade in April 1861, and the Union Navy expanded it throughout the war.