The 17th Mississippi Infantry was the last Confederate unit to arrive on the field. These 600-700 fresh troops showed up late in the afternoon and tipped the balance of what had been a hard but evenly fought contest up to that point.
The Mississippians had double-timed much of the way from their positions near Leesburg and were, according to Pvt. Robert Moore, "very near run down when we got there." To let them catch their breath and to protect them from still heavy Union fire, Colonel Winfield Scott Featherston ordered his men to lie down. Pvt. Calvin Vance later wrote that Featherston's order "was obeyed with great alacrity; no lizards ever got closer to the ground than we did...the Mine balls came screaming by and over us, saying, ?Where-are-you?' while we hugged old mother earth."
The 17th initially deployed just behind this point. The 18th Mississippi, split into two battalions, was to the right and the left of the 17th, the two regiments forming a broad arc. Shortly before dark they advanced, supported by an element of the 13th Mississippi, and some of the dismounted Virginia cavalrymen in what had become the battle's climatic movement. They overwhelmed the beleaguered Union troops, finally driving them into the river and shooting down on them from the crest of the bluff, only ceasing fire when it became too dark to see.