There now occurred another one of those horrible massacres which fouled the name of the French through their inability to control their savage allies. The prisoners numbered 1700, many of them civilian employees in the ship-yards, and Montcalm had pledged their safety. Notwithstanding this, more than a hundred were killed by the savages, either quickly or by the slow process of torture. The French losses in the siege were 30 killed and wounded, and the English killed in fighting numbered 150.
The artillery of the English forts at Oswego was removed to Fort Niagara and the forts were dismantled. The forts remained unoccupied until 1759, when the English advancing to the attack of Fort Niagara left a force of 500 men here to protect their rear and keep open their lines of communication. The French advanced against this small command and would have taken it by surprise had not a priest insisted upon speaking to the troops before they went into battle. The English became apprised of the approach of the French during this delay and sallied out to attack them, with victory in the subsequent battle crowning their efforts.
In 1760 General Amherst strengthened the forts at Oswego and left a large force here which became valuable in the war against Canada. This was one of the few fortunate moves that this general made.
Fort Ontario was also an important base for the British during the war of American Independence. In 1777 the English Colonel St. Leger gathered 700 men here and was joined by Brant with 700 Indians. The combined forces marched to besiege Fort Stanwix at the head of the Mohawk River, but were defeated and pursued back to their base, where they hurriedly embarked for Montreal.
In 1783 General Washington prepared an expedition under Colonel Willett to capture Fort Ontario. The command assembled at Fort Stanwix and marched for Oswego. When within a few miles of the fort their presence was discovered and made known to the British by some wood-cutters, and Colonel Willett, on learning that his chance of taking the post by surprise was gone, marched back to Fort Stanwix without making an attack. Peace was soon declared and no further operations were conducted.
The post was transferred to the United States in 1796, with the other frontier posts which Great Britain had held. From then until the outbreak of the War of 1812 it was allowed to fall into decay, and at the beginning of that conflict was but partially armed and quite unable to withstand an enemy. The English, hearing of its condition, and hearing, moreover, of the presence in the fort of large quantities of stores of all kinds, sent a fleet with 3000 men against the place.
The British force appeared before the town May 5, 1814. The Americans prepared a battery on shore and gallantly repulsed efforts at landing, until at length the British, through pure force of numbers, were able to accomplish this first step. The Americans then retreated up the river in good order, burning the bridges in their rear. Their number was 300. The British, baffled in taking any prisoners, burned the barracks, spiked the guns and retired. The American loss was 6 killed, 38 wounded and 24 missing. The British loss was 235. From that time to the present Fort Ontario has remained in possession of the United States.
The years saw the town of Oswego grow up around Fort Ontario. The fort was rebuilt of wood in 1839 and of stone in 1863. In 1901 the garrison was withdrawn and the old fort is now a public reservation for the use of the citizens of Oswego, its days of military life probably ended forever.