With the huge movement of both civilian and military populations in and out of nearly every major seaport from Savanannah to Boston between 1775 and 1781, urban slaves had unprecedented chances for making their personal declarations of independence and for destabilizing the institution of slavery. Similarly, as loyalist and patriot militia crisscrossed the countryside plundering the farms and plantations of their enemies, slaves found ways of tearing holes in the fabric of slavery.

A turning point came in November 1775, when the royal governor of Virginia, Lord John Dunmore, issued a dramatic proclamation that guaranteed freedom to slaves and indentured servants who escaped their masters and reached the King’s forces. Against this concrete offer of unconditional freedom, slaves could only hope that the American patriots would respond to calls for the end of slavery advocated by the first abolition society established in Pennsylvania just a few months before. Waiting for freedom as a gift at some indeterminate point turned out to be a poor substitute for immediate freedom. When word of Dunsmore’s proclamation quickly spread through the South, hundreds of slaves fled their masters to British lines where officers formed them into the Black Regiment of Guides and Pioneers. Some marched in uniform with the inscription on their breasts, “Liberty to Slaves.”

Dunsmore’s proclamation galvanized the South against England, for it conjured up a vision of a large body of free Negroes, armed by the British, abroad in the land. “Hell itself,” wrote one southerner, “could not have vomited anything more black than this design of emancipating our slaves.” But thousands of slaves did find freedom by reaching British lines. The black war for independence occurred in every part of the country  and was especially intense whenever slaves were within running distance of the British army or navy.

In the South, the pursuit of freedom through flight to the British was so large that the British army was often hard-pressed to provision the fleeing slaves. Thomas Jefferson, Virginia’s wartime governor, reported that 30,000 slaves fled their masters during the British invasion of Virginia in 1780-81. Twenty-three of Jefferson’s slaves fled his plantation to join the British, as did 17 of Washington’s slaves. In South Carolina and Georgia, probably one-third to one-half of the enslaved fled to the British during the southern campaigns between 1779 and 1781. Without doubt the American Revolution marked the greatest slave rebellion in the long history of American slavery.

–Gary B. Nash, “Forgotten Americans,” in The American Revolution, Official National Park Service Handbook (undated), pp. 75, 78.