The Fenian insurgents, led by Brigadier General John O'Neill, a former Union cavalry commander who had specialized in anti-guerrilla warfare in Ohio, secured boats and transferred some 800 men across the Niagara, landing above Fort Erie, before dawn on June 1, 1866.
O'Neill spent the first day trying to rally the local citizenry to the Fenian cause and to commandeer supplies for his mission, but his force was plagued by desertions almost from the outset.