From the Washington Post, a story about Civil War hero Robert Smalls: http://www.washingtonpost.com/local/civil-war-hero-robert-smalls-seized-the-opportunity-to-be-free/2012/02/23/gIQAcGBtmR_story.html?tid=pm_pop
Smalls became skilled at working on ships, eventually advancing to the position of pilot. In 1861, he was hired to work on a steamer called the Planter, which was used to transport cotton to ships headed to Europe. But once the Civil War started, the Confederates seized it for use as an armed transport vessel.
Smalls knew how to navigate. He knew that the white crew trusted him. He had his eye on freedom, and all he needed was an opportunity.
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“They were going to seize the ship,” said Lawrence Guyot, a black-history expert in Washington. “It was dangerous. It was daring. It was unprecedented. And when they accomplished it, it was used to demonstrate that blacks could be brave and strategic in pulling off military maneuvers. Because of what happened on the Planter, Abraham Lincoln decided to let African Americans join the fight in the Civil War.”