A large attack by artillery took place before the infantry charge. The Confederates hoped the artillery attack would make the Union weaker. It did not work well. About 12,500 men in nine infantry brigades marched over open fields for three-quarters of a mile under heavy Union artillery and rifle fire. Some Confederates were able to get past the low stone wall that many of the Union defenders hid behind. However, they could not hold this area. The Union pushed the Confederates back. Over 50% of the Confederate soldiers on the charge suffered casualties. This defeat ended the three-day battle and Lee's campaign into Pennsylvania. Years later, when asked why his charge at Gettysburg failed, General Pickett said: "I've always thought the Yankees had something to do with it."