After his Commander had been wounded and some Confederates had breached the stone wall at the Battle of Gettysburg, Haskell rallied the men and repelled General Pickett’s Charge, inflicting a decisive defeat that ended the three-day battle.
Gibbon later wrote, "I have always thought that to him, more than to any one man, are we indebted for the repulse of Lee's assault." Haskell acted without direction from superior officers, and in doing so made history.