The Rebel Invasion of Pennsylvania.; The Truth Regarding Some Important Historical Facts.
Not long after the Battle of Gettysburg a book about the battle was already in publication. The story of Big and Litte Round Tops however was not the story of Vincent's
Third Brigade, but the book told another story about Crawford's Pennsylvania Reserves. James Clay Rice, who would die at the battle of Spotsylvania the following year,
was able to weigh in on the matter before his death.
In a responce, that I may have been the first to stumble across, Fisher gives a rare look into his reasons for leaving Chamberlain alone,
"On my way up the hill I got an intimation, coming from some rebel prisoners, that a movement was about being made by the enemy
to send a brigade down the valley between Round Top and Little Round Top, for the purpose of cutting off and capturing the troops on
Round Top (They having heard us go up.). I at once hastened down the hill and moved the Ninth and Tenth upon the ground
previously occupied by the Fifth and Twelfth, so as to cover the valley and prevent such a movement, should it be attempted."
A month later General Sykes would send General Crawford a letter rebuking him for his and Fisher's attempts to steal credit away from the Third Brigade.
See: Sykes to Crawford
For a comparison of sources see: Big Round Top.