Napoleon delayed the start of fighting at the Battle of Waterloo on the morning of 18 June for several hours while he waited for the ground to dry after the previous night's rain. By late afternoon, the French army had not succeeded in driving Wellington's forces from the escarpment on which they stood. When the Prussians arrived and attacked the French right flank in ever-increasing numbers, Napoleon's strategy of keeping the coalition armies divided had failed and a combined coalition general advance drove his army from the field in confusion.