Mutiny tore like wildfire through the wooden warships of the age of revolution. While commoners across Europe laid siege to the nobility and enslaved workers put the torch to plantation islands, out on the oceans, naval seamen by the tens of thousands turned their guns on the quarterdeck and overthrew the absolute rule of captains. By the early 1800s, anywhere between one-third and one-half of all naval seamen serving in the North Atlantic had participated in at least one mutiny, many of them in several, and some even on ships in different navies. In The Bloody Flag, historian Niklas Frykman explores in vivid prose how a decade of violent conflict onboard gave birth to a distinct form of radical politics that brought together the egalitarian culture of North Atlantic maritime communities with the revolutionary era’s constitutional republicanism. The attempt to build a radical maritime republic failed, but the red flag that flew from the masts of mutinous ships survived to become the most enduring global symbol of class struggle, economic justice, and republican liberty to this day.