 As the fighting played out on September 17, 1862, known as the bloodiest single-day battle in American history, the battles at Dunker Church and Burnside's Bridge proved to be too much for Lee and his Confederate army.Luckily for Lee, the arrival of A.P.Hill's troops and the mixture of McClellan's and Burnside's sluggishness, saved Lee's Army of Northern Virginia and allowed them to barely hold off the Union in Maryland.