To the Honourable Head-Quarters, left wing, 2d Division, John ARMSTRONG, Fort Erie, U. C., August 23d, 1814. Secretary of War, Washington, D. C. Sir: I have the honour to communicate, for the information of the department of war, the particulars of the battle fought at this place, on the 15th instant, between the left wing of the 2d division of the northern army, under my command, and the British forces in the Peninsula of Upper Canada, commanded by Lieutenant-General Drummond, which terminated in a signal victory in favour of the united American arms. Our position on the margin of the lake, at the entrance of the Niagara river, being nearly a horizontal plain, twelve or fifteen feet above the surface of the water, possessing few natural advantages, had been strengthened in front by temporary parapet breast works, entrenchments and abatis, with two batteries and six field pieces. The small unfinished fort, Erie, with a 24, 18 and 12 pounder, forms the north-east, and the Douglass battery, with an 18 and 6 pounder near the edge of the lake, the south-east angle of our right. The left is defended by a redoubt battery, with six field pieces just thrown up on a small ridge. Our rear was left open to the lake, bordered by a rocky shore of easy ascent. The battery on the left was defended by Captain (p. 228) Towson; Fort Erie, by Captain Williams, with Major Trimble's command of the 19th infantry; the batteries on the front, by Captains Biddle and Fanning; the whole of the artillery commanded by Major Hindman. Parts of the 11th, 9th and 22d infantry (of the late veteran brigade of Major-General Scott) were posted on the right, under the command of Lieutenant-Colonel Aspinwall. General Ripley's brigade, consisting of the 21st and 23d, defended on the left. General Porter's brigade of New York and Pennsylvania volunteers, with our distinguished riflemen, occupied the centre. I have heretofore omitted stating to you, that during the 13th and 14th, the enemy had kept up a brisk cannonade, which was sharply returned from our batteries, without any considerable loss on our part. At 6 P.M. one of their shells lodged in a small magazine in Fort Erie, which was fortunately almost empty. It blew up with an explosion more awful in appearance than injurious in its effects, as it did not disable a man or derange a gun. It occasioned but a momentary cessation of the thunders of the artillery on both sides; it was followed by a loud and joyous shout by the British army, which was instantly returned on our part, and Captain Williams, amidst the smoke of the explosion, renewed the contest by an animated roar of his heavy cannon.