The 80 guns of Napoleon's grande batterie drew up in the centre. These opened fire at 11:50, according to Lord Hill (commander of the Anglo-allied II Corps), while other sources put the time between noon and 13:30. The grande batterie was too far back to aim accurately, and the only other troops they could see were skirmishers of the regiments of Kempt and Pack, and Perponcher's 2nd Dutch division (the others were employing Wellington's characteristic "reverse slope defence").

The bombardment caused a large number of casualties. Although some projectiles buried themselves in the soft soil, most found their marks on the reverse slope of the ridge. The bombardment forced the cavalry of the Union Brigade (in third line) to move to its left, to reduce their casualty rate.