At the age of eighteen he entered his country's service as a volunteer, and served through the Revolution, participating in many of the greatest victories won by the Americans, sharing the worst hardships of the war with his fellow patriots, and laying down his arms only after Cornwallis had surrendered his sword at Yorktown.
At the beginning of the winter of 1775-1776, North Carolina was confronting the most perilous conditions which she had ever been called to face. From the north, east and west, the foe was pressing, while within her own borders the Tories were rising, and planning to join the British in the subjection of this rebellious state.
The plan formulated by the enemy was this: Sir Henry Clinton, with troops of British regulars, was to come down the coast to the mouth of the Cape Fear River, where Lord Cornwallis, who with seven regiments from England was hastening across the Atlantic, was to join him. Lord Dunmore, Royal Governor of Virginia, was to incite the slaves and indentured servants in the Albemarle district to unite with the Tories in the State; and the Indians in the western counties were to be induced to take up arms against the whites.
If these plans had matured, North Carolina would have been overpowered, but one by one they were frustrated. The battle of Great Bridge defeated Dunmore in his purpose. The Snow Campaign quieted the Indian uprising. The battle of Moore's Creek Bridge crashed the Tories, and the heavy winter storms delayed Cornwallis and prevented him from joining Clinton at the mouth of the Cape Fear.
When Lord Dunmore issued his proclamation offering freedom to the slaves and indentured servants who should join his majesty's forces, and then followed up this notice by burning and ravaging the plantations around Norfolk, Virginia, called upon her sister State for help, and Long and Sumner, from Halifax, and Warren, Skinner and Daugé from Perquimans and Pasquotank counties, hastened with their minute men and volunteers to Great Bridge, where Colonel Woodford in command of the Virginia troops, had thrown up fortifications.
Among the volunteers who were hastening to the scene of action was John Koen, of Pasquotank, a boy in years, but a man in purpose and resolution.
On December 9, 1775, the British attacked the fortifications, and the sound of heavy firing at Great Bridge, the first battle in which the men of the Albemarle section had been called to participate, was heard by the dwellers in the counties nearest Norfolk.
The story is still told by old residents of Rosedale, that John Koen's mother, who was washing the breakfast dishes when the firing began, hearing the first heavy reverberations from the cannon some thirty miles away, dropped the dish she was wiping, and in her motherly anxiety for the safety of her boy, cried out, "Dodge, John, dodge!"
Whether John dodged or not we do not know, but we do know that he bore his part manfully in this, his first battle, and shared in the victory which drove Dunmore from Virginia, and saved North Carolina from invasion from that direction, and a threatened uprising of the slaves.
On February 26, 1776, the battle of Moore's Creek Bridge was fought, which defeated the Tories in Carolina, and convinced the British that further attempts at this time to conquer the State were useless. So, toward the end of May, Clinton's fleet sailed from the mouth of Cape Fear River to Charleston, South Carolina, where his intention was to reduce that city.