During the Chancellorsville Campaign, the Eleventh Corp under General Howard was positioned on the right flank of the Union line. Howard lefted his flank up in the air. Seeing this, Confederate General Stonewall Jackson decided to attack the Eleventh Corp. The Eleventh Corp collapsed quickly and created a panic that caused the rest of the Union Army to collapse.
In the main time, the III Corp was position in the center of the Union line, its commander General Sickles decided to move his corp forward in a salient at Hazel Grove. While this salient seperated Jackson's Corp from rest of the Confederate Army, it was dangerous exposed and got attacked from both flanks, like being in a nutcracker. The III Corp also collapsed and adding to the confusing.
One the first day of the Battle of Gettysburg, the commander of the Union Army, John Reynolds was killed and the command was passed on to Howard. Howard decided to position his Eleventh Corp with flank up in the air again. Again, Confederate General Jubal Early took advantage of this and rolled up the Eleventh Corp and it made panic withdrew to the Cemetery Hill. Fortunately, General Hancock arrived in time to take replace Howard and prevented another Chancellorsville.
One the second day of battle, General Sickles again decided to move his III Corp forward in an exposed position, and even worse, he lefted a gap in the left side Union line, which included the Little Roundtop. Once again the exposed salient got attack from both sides, and again got crushed like a nut in a nutcracker, only the quick thinking General Warren who moved men ( including 20th Maine) to the Little Roundtop and General Hancock who ordered the First Minnesota into the gap left by the III Corp to buy him sometime, so he can get reinforcements. First Minnesota lost over 80% of it men, but they brought an extra eight minutes for reinforcement to arrive, thus, avoiding another Chancellorsville.
The moral to the story is "those who failed to learn from history, are doomed to repeat it"
General Sickles was directing the battle on a horse when leg was shot off by a cannon ball and was taken from the field and never commanded again. He placed the leg in a small coffin and donated it to the National Museum of Health and Medicine. Sickles die in 1914, it was noted he had visited his leg many times in the Museum! This Museum is now a part of the Walter Reed Hospital.
Howard and Eleventh Corp redeemed themselves when they helped General T. Sherman in capturing Atlanta and General Hooker in capturing the Lookout Mountain in Chattanooga. Later in life, Howard founded the famous Howard University in Washinton DC in 1867. In 1877, the Nez Perce led by Chief Joseph were trying to escape to Canada. Howard led an army in pursue, the Nez Perce managered to stay miles ahead of Howard, until Nelson Miles Army came along and blocked their path only miles from the Canadian border. Howard was on hand to accept Chief Joseph's famous surrender "My heart is sick and sad. From where the sun now stands I will fight no more forever."