Complacency endangers history.  The first plausible answer is not always the correct or solitary one, yet all too often we content ourselves with simplistic solutions to murky questions.  Civil War historians have grappled with the Battle of Chancellorsville for nearly 150 years, and we (surprisingly) we still have very simple rejoinders for why Joseph Hooker and the Army of the Potomac lost a struggle which they entered into with every advantage.  Joe Hooker lost the Battle of Chancellorsville because of his own arrogance and errors.  Joe Hooker lost Chancellorsville because he was no match for the Robert E. Lee and the Army of Northern Virginia.  Fighting Joe Hooker lost Chancellorsville simply because Fighting Joe Hooker lost confidence in himself.

In all likelihood, there are grains of truth to all these theories.  Yet one should be careful of placing too much emphasis on anyone of them singularly.  Instead, I wish to focus on a forgotten answer to the age old question of what went wrong for the Union army and Joe Hooker in May of 1863.  On the morning of May 3rd, General Hooker was wounded, probably suffering a severe concussion received from Confederate artillery fire.  This event, minimized and overlooked in many accounts of the battle, perhaps played a far greater role at Chancellorsville than history has given credit for.