The attack began at 5:30 am on Easter Monday, 9 April 1917. Light field guns laid down a barrage that advanced in predetermined increments, often every three minutes, while medium and heavy howitzers established a series of standing barrages against known defensive systems further ahead. The 1st, 2nd, and 3rd Canadian Divisions quickly captured their first objectives. The 4th Canadian Division encountered a great deal of trouble during its advance and was unable to complete its first objective until some hours later. The 1st, 2nd, and 3rd Canadian Divisions captured their second objective by approximately 7:30 am. The failure of the 4th Canadian Division to capture the top of the ridge delayed further advances and forced the 3rd Canadian Division to expend resources establishing a defensive line to its north. Reserve units from the 4th Canadian Division renewed the attack on the German positions on the top of the ridge and eventually forced the German troops holding the southwestern portion of Hill 145 to withdraw.