The stakes that morning were far larger than one sloop's survival. Paul Marin de la Malgue was leading a relief convoy of four French vessels and fifty Mi'kmaq canoes carrying some 1,200 fighters toward the besieged Fortress Louisbourg on Cape Breton Island. New England forces, numbering about 4,000 men, had been pressing the siege for weeks against roughly 1,500 French defenders. The governor of Ile Royal, Louis Du Pont Duchambon, later acknowledged that had Marin's convoy broken through, the New Englanders would likely have abandoned the siege altogether. The entire colonial balance of power in Atlantic Canada hinged on whether a ragged flotilla of reinforcements could thread through the waters of Northumberland Strait.

Donahew's Resolution carried just twelve guns and a crew of fifty. His two companion vessels, Captain Daniel Fones in the fourteen-gun Tartar and Captain Robert Becket in the six-gun Bonetta, had left him to investigate smoke from what they thought was a French encampment onshore. Alone and surrounded when the wind fell off, Donahew opened up at ten o'clock in the morning. In his own account, published in the Pennsylvania Gazette that August, he reported firing two hundred rounds from his four-pounders, fifty-three rounds from his three-pounders, and keeping his swivel guns and small arms playing on the enemy without pause. For two hours the Resolution fought alone against four vessels and dozens of canoes, the French closing to boarding distance before Fones and Becket, having heard the gunfire, came racing back. Their arrival broke the French nerve. Marin's convoy scattered, retreating first to nearby Gouzar and then to Tatamagouche itself.

The French built hasty defenses on land at Tatamagouche, expecting the New Englanders to press their advantage. When another colonial vessel appeared a few days later, the Huron contingent, apparently shaken by their losses, abandoned the convoy and headed back toward Quebec. Without Marin's 1,200 reinforcements, Fortress Louisbourg was doomed. Thirteen days after the naval battle, on June 28, 1745, Duchambon surrendered the fortress to the New England besiegers. It was one of the most significant colonial victories of King George's War, and the small engagement off Tatamagouche had made it possible. Three ships and a captain's audacious bluff had prevented a relief force that outnumbered the convoy escorts by more than ten to one.

Donahew's courage cost him his life just two weeks later. After the fall of Louisbourg, he and Fones encountered Marin again near the Strait of Canso. Donahew went ashore with eleven men and was immediately surrounded by three hundred Mi'kmaq and allied Indigenous warriors. The captain and five of his crew were killed on June 29, 1745, and the remaining six were taken prisoner. On July 19, the Resolution sailed slowly into Louisbourg harbour with her colors at half-mast. The story of Donahew's death spread rapidly through the garrison, casting a pall over what should have been a triumphant occupation. Fones brought the Tartar safely home to Rhode Island, where two of the sloop's cannons eventually found a permanent resting place on the lawn of the Newport Historical Society.

In August 1939, the Historic Sites Monument Board erected a monument at Tatamagouche overlooking the harbour where the battle took place. The quiet village on the Northumberland Strait shore gives little outward sign of its role in reshaping colonial North America. The waters are calm most days, the harbour modest and unassuming. But for a few hours on a June morning in 1745, this was one of the most consequential stretches of water on the continent, where a lone sloop captain's refusal to surrender changed the course of a war.