Excerpts from Books and Wikipedia
"On his left flank he was being attacked by the Prussians under Marshal Blucher, who had maneuvered to aid Wellington. In the final attempt to drive his adversary from the field, Napoleon launched the Imperial Guard, his most experienced soldiers and his final reserve, at the Allied position. But in the face of British musketry, the Imperial Guard turned and fled. Napoleon had lost his final battle." [Furtado: 1001 Days]