The Massachusetts authorities conferred upon him the commission of Colonel with directions to raise 400 men and make an attempt to capture Ticonderoga. He repaired to Castleton, Vermont, where he met Col. Allen. On the 10th of May, 1775, this fortress surrendered at discretion. On the 6th of September of that year he commenced his march for Canada through the dense forest with 1000 men from New England consisting of infantry, one company of artillery and three companies of riflemen. A portion of his troops were obliged to return for want of provision to sustain them all, through the wilderness. The balance endured the severest hardships on the march and arrived at Point Levi opposite Quebec at the end of six weeks. But from the fact that Arnold had sent a letter forward to a friend by an Indian who betrayed his trust by giving information of the approaching troops it is believed Quebec would have been easily captured. To prevent this all means of crossing the river had been removed and the fortifications put under rapid improvement. It was not until the night of the 14th of October that he led his little band of 700 men up the heights that had been surmounted by Wolfe and formed them near the memorable plains of Abraham. The city had become so well fortified that the summons to surrender was treated with contempt. To attack with so small a force would be a reckless waste of human life. In a few days he marched to Point aux Trembles twenty miles above Quebec to await the coming of Gen. Montgomery who arrived on the first day of December. A siege upon the city was immediately commenced which was successfully resisted. On the morning of the 31st of that month a simultaneous assault was made on two sides of the city in which Montgomery was killed and Arnold severely wounded in the leg. Officers and men behaved with great gallantry. No other assault was attempted--the blockade was continued to May 1776. On the 18th of June Arnold withdrew from Canada. He subsequently commanded the small fleet on Lake Champlain and exhibited great skill and bravery.