america is in the midst of commemoration of the anniversary of the civil war. and consider the battle of g gettysbu gettysburg. and with us to talk about it. mike barnicle, he was there and pulitzer winning historian jon meacham. by the way, he was cheering for lee. best selling author, doris kaerearns good win. let's begin with you, jon, why did gettysburg matter so much? >> it turned lee's army back and ended the invasion of the north and was the turning point of the war. at that point, though it was going to be difficult and bloody