On August 15th, gunners of the British Canadian Provincial Marine set up a battery on the Canadian shore of the Detroit River and began bombarding Fort Detroit, joined by two armed vessels in the river. In the early hours of the morning of August 16th, Tecumseh’s warriors crossed the river about 5 miles south of Detroit. They were followed after daybreak by General Brock’s force, divided into three small brigades.
Brock originally intended to occupy a fortified position astride Hull’s supply line and wait for starvation and bombardment to force the Americans to surrender or come out to fight, but he then learned that on the previous day, Hull had sent a detachment of 400 men under Colonels Cass and McArthur to escort a convoy to Detroit via a backwoods trail some distance from the lake and river, and this detachment was only a few miles from the British rear. Brock advanced immediately against the rear of Fort Detroit, the side furthest from the river where the defenses were weakest.
As the British bombardment began to cause casualties, Hull despaired of holding out against a force which seemingly consisted of thousands of British soldiers and, hearing Indian war cries, began to fear a slaughter. Women and children still lived within the fort. Against the advice of his subordinates, Hull hoisted a white flag of surrender. He sent messengers to Brock asking for three days to agree on terms of surrender. Brock replied he would allow him three hours. Hull surrendered his entire force, including Cass’s and McArthur’s detachment and the supply convoy.