Fought this day in 1776. The Americans were in retreat when (and I quote the wikipedia entry)
British troops made a tactical error by having their bugler sound a fox hunting call, "gone away," while in pursuit. This was intended to insult Washington, himself a keen fox hunter, having learned the sport from Lord Fairfax during the French and Indian War. "Gone away" means a fox is in full flight from the hounds on its trail. The Continentals, who were in orderly retreat, were infuriated by this and galvanized to hold their ground. After flanking the British attackers, the Americans slowly pushed the British back. After the British fled, Washington had his troops end the chase. The battle went a long way to restoring the confidence of the Continental Army after suffering several defeats. It was Washington's first battlefield victory of the war.
42nd Highlander officer 1776 by G Embleton here