As I have ever entertained Hopes that an Accommodation might have taken Place between Great-Britain and this colony, without being compelled by my Duty to this most disagreeable but now absolutely necessary Step, rendered so by a Body of armed Men unlawfully assembled, bring on His Majesty’s [Tenders], and the formation of an Army, and that Army now on their March to attack His Majesty’s troops and destroy the well disposed Subjects of this Colony. To defeat such unreasonable Purposes, and that all such Traitors, and their Abetters, may be brought to Justice, and that the Peace, and good Order of this Colony may be again restored, which the ordinary Course of the Civil Law is unable to effect; I have thought fit to issue this my Proclamation, hereby declaring, that until the aforefaid good Purposes can be obtained, I do in Virtue of the Power and Authority to me given, by His Majesty, determine to execute Martial Law, and cause the same to be executed throughout this Colony: and to the end that Peace and good Order may the sooner be [effected], I do require every Person capable of bearing Arms, to [resort] to His Majesty’s standard, or be looked upon as Traitors to His Majesty’s Crown and Government, and thereby become liable to the Penalty the Law inflicts upon such Offences; such as forfeiture of Life, confiscation of Lands, &c. &c. And I do hereby further declare all indentured Servants, Negroes, or others, (appertaining to Rebels,) free that are able and willing to bear Arms, they joining His Majesty’s Troops as soon as may be, for the more speedily reducing this Colony to a proper Sense of their Duty, to His Majesty’s Leige Subjects, to retain their [Quitrents], or any other Taxes due or that may become due, in their own Custody, till such Time as Peace may be again restored to this at present most unhappy Country, or demanded of them for their former salutary Purposes, by Officers properly authorised to receive the same.Given under my Hand on board the ship William, off Norpole, the 7th Day of November, in the sixteenth Year of His Majesty’s Reign.Dunmore.(God save the King.)
By November 14, 1775, when John Murray, Earl of Dunmore and royal governor of Virginia, issued his proclamation, his plan to offer freedom to slaves who would leave their patriot masters and join the royal forces was already well underway.
Dunmore understood that such an act would have a wide-ranging effect. Not only would it disrupt production, it was also feed the growing fear among the colonists of armed slave insurrections. Planters would be distracted from waging war against Britain by the necessity of protecting their families and property from an internal threat. At the same time, Dunmore's own force of 300 soldiers, seamen and loyalist recruits, cut off from the support of British troops in Boston, would be reinforced by black fighting men and laborers.
Word of Dunmore's plan was known as early as April, when a group of slaves presented themselves to him to volunteer their services. He delayed the decision by ordering them away, but the Virginia slaveholders' suspicions were not allayed. On June 8, 1775, Dunmore left Williamsburg, taking refuge aboard the man-of-war Fowey at Yorktown. Over the next five months, he reinforced his troops by engaging in a series of raids and inviting slaves aboard the ship. On November 7, Dunmore drafted a proclamation, and a week later he ordered its publication. It declared martial law and adjudged the patriots as traitors to the Crown; more importantly, it declared "all indented servants, Negroes, or others...free that are able and willing to bear arms..."
Response from the colonists was immediate. Newspapers published the proclamation in full, and patrols on land and water were intensified. Throughout the colonies, restrictions on slave meetings were tightened. The Virginia Gazette warned slaves to "Be not then...tempted by the proclamation to ruin your selves" and urged them to "cling to their kind masters," citing the fact that Dunmore himself was a slave holder.
In December, the Virginia Convention issued its own proclamation as a broadside, declaring that runaways to the British would be pardoned if they returned in ten days, but would be severely punished if they did not. The document began with a reminder of the penalty for slave insurrection -- death without benefit of clergy -- though in practice, it was used sparingly during the war.
By then, 300 black men had been inducted into "Lord Dunmore's Ethiopian Regiment," armed, and outfitted in military uniforms inscribed with the words "Liberty to Slaves." By early June, however, Dunmore's forces had been decimated by smallpox and the patriot's defenses. In August, the British destroyed over half of their own ships and sailed out of the Potomac, taking the 300 healthiest blacks with them.
Although probably no more than 800 slaves actually succeeded in reaching Dunmore's lines, word of the proclamation inspired as many as 100,000 to risk everything in an effort to be free. (soruce: PBS)