Short answers, pulled from the story.
King Cotton was a pre-Civil War slogan and strategy holding that Southern control over cotton exports would make an independent Confederacy economically viable and force Britain and France to support it militarily. By 1860, Southern plantations supplied 75% of the world's cotton and the crop represented almost 60% of all American exports, valued at nearly $200 million a year, giving Confederate leaders confidence in the theory.
Senator James Henry Hammond of South Carolina made the phrase famous in a Senate speech in 1858. He argued that no power on earth dared make war on cotton, and predicted that three years without Southern cotton would topple England and carry the civilized world with her.
Britain had strong anti-slavery public sentiment, surplus cotton stockpiles in spring 1861, and found alternative sources in India, Egypt, and Brazil. Intervening would also have risked war with the United States, the loss of American markets and grain supplies, and threatened Canada and British merchant shipping, making the gamble unattractive.
Cotton production in British India rose by 70% during the conflict. Brazilian annual cotton exports increased 400%, from 12,000 to 60,000 tonnes, between 1860 and 1870. Egypt also expanded output, and the Manchester Cotton Supply Association worked through a British-owned Buenos Aires newspaper to encourage Argentine farmers to export cotton to the United Kingdom.
In early 1861, Southern planters spontaneously withheld cotton from export without government direction. In 1862, the Confederate Congress went further by authorizing the burning of cotton in areas where Union forces were advancing, to prevent it from falling into enemy hands.
By the summer of 1861, the US Navy blockaded every major Southern port and shut down more than 95% of all Confederate trade. Some cotton escaped through blockade runners or via Mexico, but the volume was insufficient to sustain Confederate cotton diplomacy. As Union armies advanced into cotton regions in 1862, the United States took possession of available cotton and sold it to European buyers or sent it to Northern mills.