Following on from Ligny and Quatre Bras, Part II starts by focusing on the concentration of the Allies on the ridge of Mont St Jean and the plans of the opposing armies. While the guns of the Grand Battery thundered in the centre, French columns bore down on the Hougoumont chateau and farm complex, which protected Wellington's flank held by the Guards and their German allies. Thus began an epic 'battle within a battle' that sucked away valuable troops from Napoleon's main attack, causing Wellington to declare that 'the battle turned on the closing of the gates at Hougoumont'.Meanwhile D'Erlons Corps attempted to bludgeon its way through Wellington's centre, not knowing that the British and Dutch line was in waiting on the reverse slope. Upon seeing the French advance, the British released a disciplined volley of musket fire that checked the French. A further brilliantly timed charge by the Household and Union Cavalry Brigades finally saw the French off.