I am breaking 5 or so years of silence to begin the "Chamberlain was the true hero of Gettysburg" discussion.
>(no, not because I saw the Ted Turner movie)> Flame away!
Chamberlain was the regimental colonel of the 20th Maine at the time of the Battle of Gettysburg. He was assigned the job of holding the Federal left flank in the battle and he did a superb job of his assignment. The actions of Chamberlain and his men were in any sense of the word, heroic.
Yet how does his accomplishment stack up against Hancock's? When Hancock arrived on the field at Gettysburg, Reynolds had been killed and he took operational command of the army until Meade could come up (which didn't happen until late the night of the 1st.) He immediately saw that holding Cemetary Ridge was key at Gettysburg -- it was a strong, defensible position but it also placed the Federal army between the Confederates and Washington DC, their supposed objective. He carefully positioned the troops he had at his disposal about as well as he could have, and that turned out to be as good as was needed -- Lee attacked for two days and could not dislodge them. Moreover, Hancock was personally involved in command at the line level, even after his horrific injury (as described in the article above).
I contend that Hancock was indeed absolutely critical to the Federal victory. This takes nothing away from Chamberlain, who after all, received the Congressional Medal of Honor for his actions. Chamberlain's actions saved the Federal left flank; Hancock's actions saved the Army of the Potomac.