"Gettysburg" was a movie, remember that. I have studied the battle for a number of years. My focus is Massachusetts units at Gettysburg. About 1/2 of the movie is fiction. The title should have been "The 20th Maine at Gettysburg." Everyone praises the 20th's exploits on Little Round Top and how Chamberlain saved the Union from sure defeat.
In the movie, after the fighting had stopped, the colonel from the 83 PA goes up to Chamberlain and says "Colonel we watched what you did". The left flank of the 83rd was only partially engaged. If the 20th had fallen, undoubtedly the rest of the 83PA would have moved in. How many reinforcements did the South have on hand to rush up and, in historians words "Roll up the Union flank and destroy the Army of the Potomac." There is one problem with this statement. The attack on Little Round Top started about 6:00PM. Around 4:00PM Meade and his staff are on the south slope of Cemetery Hill. Meade noticed a large cloud of dust rising up in the direction of the Emmitsburg Road. He spots a corps flag appearing from out of the dust. He is claimed to have stated, "Thank God it's the 6th Corps." This very scene is depicted in the movie. It is one of the few historically accurate parts. The 6th Corp had just accomplished a forced marched over 25 miles. Anyone know where their line of battle was along Cemetery Ridge? If you said, anchored on the north facing slope of Little Round Top, you'd be correct.
Why was the arrival of the John Sedgwick's 6th Corps so vital to Meade and the Army of the Potomac? Not only was Meade's Army now complete, it also meant the largest corps in his army was now at Gettysburg. The Sixth Corps contained 12,000 men. Larger then any reinforcements in Lee's reserve at that time in the battle. Yes, they had just made a brutal march in the July heat, but, they had 2 hours to rest up. Even if half of the Sixth had been able to respond to a Confederate assault, it clearly would have resulted in a rout of the southern attack.
One question I ask people when I'm at the Copse of Trees, "Did anyone see the movie GETTYSBURG"? Hands go up all over. In the movie, the fighting has stopped on Little Round Top. Chamberlain is told that he will be placed in the quietest spot in the line, near the Copse of Trees. Of course we all know what happened the next day. Longstreet's Assault, otherwise know as Pickett's Charge. One thing some people don't know, every Union regiment that was at Gettysburg have placed monuments or markers where they were in position during the battle. Some have two, three even four markers. I ask them to show me the 20th's position on the line we are presently standing.
There is none, don't waste your time. It was Hollywood saying "Damn history put the 20th here". Never let the facts stand in the way of a good story. In fact the 20th was moved that night. They were put into a position northeast of the Sixth Corp. Fighting at Gettysburg was over for them.