On April 19, 1775, British and American soldiers exchanged fire in the Massachusetts towns of Lexington and Concord. On the night of April 18, the royal governor of Massachusetts, General Thomas Gage, commanded by King George III to suppress the rebellious Americans, had ordered 700 British soldiers, under Lieutenant Colonel Francis Smith and Marine Major John Pitcairn, to seize the colonists' military stores in Concord, some 20 miles west of Boston.

A system of signals and word-of-mouth communication set up by the colonists was effective in forewarning American volunteer militia men of the approach of the British troops. Henry Wadsworth Longfellow's poem "Paul Revere's Ride" tells how a lantern was displayed in the steeple of Christ Church on the night of April 18, 1775 as a signal to Paul Revere and others

One if by land, and two if by sea;
And I on the opposite shore will be,
Ready to ride and spread the alarm
Through every Middlesex, village and farm,
For the country folk to be up and to arm.

At Lexington Green, the British were met by 77 American Minute Men led by John Parker. At the North Bridge in Concord, the British were confronted again, this time by 300 to 400 armed colonists, and were forced to march back to Boston with the Americans firing on them all the way. By the end of the day, the colonists were singing "Yankee Doodle" and the American Revolution had begun. [...]

By 1777, "Yankee Doodle" had certainly become an unofficial American anthem. Following General Burgoyne's surrender of British troops to the Continental Army on October 17, 1777, British officer Thomas Anburey wrote:

. . . the name [of Yankee] has been more prevalent since the commencement of hostilities. . . . The soldiers at Boston used it as a term of reproach, but after the affair at Bunker's Hill, the Americans gloried in it. Yankee Doodle is now their paean, a favorite of favorites, played in their army, esteemed as warlike as the Genadier's March -- it is the lover's spell, the nurse's lullaby . . . it was not a little mortifying to hear them play this tune, when their army marched down to our surrender. [...]