At first light on May 5th the lookouts at Fort Oswego sighted the British and passed the word quickly to Melanthon Woolsey and Lieutenant Colonel George Mitchell, Third U.S. Artillery Regiment, who hurried to see for themselves.
The situation was a difficult one since they were ordered to protect the naval stores that had been accumlating at the fort earmaked for Sacket's Habour, but their defensive force was small and their tactical position was weak.
Colonel Mitchell had 290 men under his command, they had been part of General Brown's army at Batavia New York until they were ordered to defend Fort Oswego.
They had arrived on April 30th and moved into the fort atop the hill on the eastern shore of the bay. The British had built Fort Oswego almost a century before, and the site had been formidable. But over the years it's defensive fortifacations had disappeared. There still were some low buildings and barracks standing in the compound, and the Americans had five small calibre guns on hand, but all lacking proper carriages and three of them without trunnions.
Mitchell's gunners built the carriages and platforms for the ordnance, installing three to face the lake and the others toward the long glacis that stretched to a landing place east of the fort. They also built pickets to replace the old ones that had once skirted the fort.
As the British came into view the American commander decided to keep his men out of sight until he knew what the British intentions were. He did have one of his companies standing ready to man the guns, the others would be used as infantry.
Commandant Woolsey and Lieutenant Colonel George Mitchell decide to stand and fight the best they could, but agreed that if they faced being captured they would retrest to Fredericksburgh.
The British had been making their slow advance all morning, then they stopped just beyond the range of the American guns and started to bring around the landing boats. After one attempt to load the landing craft was aborted due to a risk of a bad storm, the British were able to try landing once more at 6:00 a.m. the guns onboard the British ships opened up chasing away the American militia. Mitchell's two batteries opened fire back at the British ships while the American infantry was safely behind the thick walls of the fort.
Captain Popham brought his ship the "Niagara" in close to the fort and anchoed. The Niagara now pounded the Americans with their broadside of nine 32 - pdrs and a single 24 - pdr and 18 pdr guns. Using a shot oven to heat their shot until it was nearly redhot, the American gunners returned the British fire and set the British ship on fire three times.
Master Richardson, while trying to put out one of the fires soon realized that one of the American cannonballs had quickly tore away his left arm, he later had an amputation at the shoulder joint. Crew members took him below. The British surgeon was able to save his life.
The British landed about 2:00 p.m. but were not quite on shore when their officers, setting an example for their men jumped off the boats and sank nearly out of sight.
Making it to shore the Royal Marines, De Watteville Regiment and the Glengarry Light Infantry checked their ammunition only to find that nearly all of it was ruined by their advance through deep water, so they all fixed bayonets. The American forces were firing well aimed vollys from the woods and the glacis so Lieutenant Colonel Fischer ordered the Glengarries to clear the woods of the enemy, which they did quicky.
On the other side of the fort the British were making a second landing and getting ready to charge up the hill and dislodge the American from the main battery, this was being lead by Captain Mulcaster.
Back at the first landing area, Colonel Fischer gave the order for the whole force to advance quickly and charge up the hill. The British could not fire their muskets as all their ammunition had been ruined while they landed, while they advanced the Americans continued to fire devastating vollys on them. The British continued forward bayonets fixed. The American vollys were knocking down dozens of British soldiers. Onr Captain and six marines were killed and thirty-three others suffered wounds. The De Wattevilles Regiment lost eight killed and twenty wounded. The Glengarry Light Infantry were a bit more fortunate with only nine men wounded.
Back on the opposite side of the fort Captain Mulcaster's seamen landed and quicly made their way up toward their objective. Armed with pikes and cutlasses they sought to over power Mitchell's gunners who were defending themselves with muskets. Captain Mulcaster was leading the charge, when he watched an American aim at him and pulled the trigger. Mulcaster was not able to move out of the way in time to avoid the musket ball, which slammed through his leg sending him crashing to the ground. The seamen rallied and continued up into the American battery all the while under heavy fire.
Back on the eastern side of the fort the British were having a hard time with the American defenders who were inspired by the faltering British line. A wave of British Marines managed to make their way into the northwest corner and ran down into the fort, while the sailors beat their way into the battery. The American Captain Mitchll knew at this point his forces were being over powered and ordered a retreat.
It was about 30 minutes since the British landed and one of the British seamen was making his way to the flag pole in the center of the fort, he jumped up onto the pole and started to scale it. The Americans, angered by this sight started pouring volleys of musket balls at the man, for they knew what he was about to do. More and more Americans began firing at him, hitiing him a number of times. Never the less he continued up the pole and reaching up tore down the massive Stars & Stripes flag from the nails that held it to the pole, he let it fall to the ground as the British forces cheered loudly.
The Americans made their retreat with whatever wounded could walk , they scuttledthe last of the boats so they would not fall into British hands and headed for Fredericksburgh.
Fort Oswego and the surrounding village fell to the British, they secured the area and sent reserves to shore to help with the many tasks, which included tending to the wounded, dead and prisoners. They also found an American captain and twenty-five or so rank and file who were dead and the British buried them. Twenty-five American prisoners were transported to the British warships.
The afternoon and evening of May 6th the British transported all the goods they captured from the Americans at Fort Oswego to their warships.
The items siezed were four 24 pdr and three 32 pdr long guns, more than 300 shot of all description and calibres. Some of the items were taken from some of the boats the Americans had scuttled has they retreated. Also the schooners "Growler" and "Penelope"