If you ever visit the US Capitol, you'll find there a very fine painting of an incident that took place during the Barbary Wars, the series of conflicts fought by the United States in the late 18th and early 19th Centuries against the marauding pirates of the North African Coast. When the Marines sing about "...to the shores of Tripoli..." this is the war they mean.
In one of the numerous ship-to-ship scuffles, Captain Stephen Decatur was leading a boarding party onto the deck of an enemy ship. In the confusion and smoke of the hand to hand fighting, he was beaten to his knees, and as he was getting up a pirate rushed over, and raised his enormous scimitar, to lop off Decatur's head. This would surely have ruined Decatur's day, had the pirate succeeded; but Decatur was saved when a seaman named Rueben James interposed himself under the scimitar and took the blow, sacrificing his life for his Captain. The painting in the Capitol depicts the instant at which James took his action.
The United States Navy has certain conventions on naming of ships: destroyers are named after naval heroes. There was eventually a destroyer named USS Rueben James, after the heroic seaman. She was one of the first American ships sunk in the Second World War, torpedoed without warning by a German U-boat off Cape Hatteras.
