The Union blockade was a military strategy employed by the Northern states during the American Civil War to prevent the Southern states from trading with foreign nations. By blocking ports and controlling waterways, the Union aimed to cut off supplies, including food and weapons, to the Confederate states, weakening their ability to sustain the war effort. This blockade was part of the larger strategy known as the Anaconda Plan, which sought to suffocate the Confederacy economically and militarily. The effectiveness of the blockade increased over time, leading to significant shortages in the South and contributing to the eventual defeat of the Confederate States.