Some of his newspaper essays attracted the attention of General Alexander Hamilton, to whom he became secretary while that officer was acting General-in-Chief of the army raised in anticipation of a war with France. When those war clouds disappeared Brown went to northern New York, purchased lands on the banks of the Black River, not far distant from Sackett’s Harbor, and founded the flourishing settlement of Brownsville, where he erected the first building within thirty miles of Lake Ontario. There Brown became county judge; colonel of the local militia in 1809; brigadier general in 1810; and, in 1812, received the appointment of commander of the frontier from Oswego to Lake St. Francis, a line two hundred miles in extent. During the War of 1812–14, he performed most conspicuous service, receiving two severe wounds in battle. At the second attack upon Sackett’s Harbor, May 27, 1813, when the news of the approach of the British squadron reached there Colonel Backus was in command. General Jacob Brown was at his home, a few miles distant. He was notified and arrived before dawn of the 28th. He sent expresses in all directions to summon the militia to the field, and fired guns to arouse the inhabitants. As rapidly as the militia came in they were armed and sent to Horse Island, where it was expected the enemy would attempt to land. On the appearance of some American gun boats the British squadron went out on the open lake. But when the enemy discovered the real weakness of the defenders, the squadron returned on the morning of the 29th and landed a large force on Horse Island. The militia had been withdrawn from the island to the mainland, and fled at the first fire of the invaders. This disgraceful conduct astonished General Brown, who rallied his troops, when he discovered the store houses and a ship in flames, set on fire by Americans who believed their militia was in full retreat. This caused General Brown to redouble his exertions to rally the militia. He succeeded, and so turned the fortunes of the day in favor of his country. When Sir George Prevost, mounted on a high stump, saw the rallying militia on his flank and rear, he believed them to be American reinforcements and sounded a retreat. For his conduct in the defense of Sackett’s Harbor, Brown was made a brigadier in the United States Army. General Brown made the only redeeming movement in Wilkinson’s disgraceful expedition down the St. Lawrence River against Montreal, November, 1813. Brown captured and held the post at the foot of the rapids, which movement permitted the union of the several armies, or the defeat would have been even more disastrous. General Brown was severely wounded at the repulse of the British at Fort Erie, August 15, 1814.