"This had two effects: it greatly diluted the concentrated defensive posture of his corps by stretching it too thin, and it created a salient that could be bombarded and attacked from multiple sides. About this time (3 p.m.), Meade called a meeting of his corps commanders. Sickles did not appear. An aide to Brig. Gen. Gouvernor K Warren soon reported the situation. Meade and Warren rode to Sickles' position, where Meade demanded an explanation from the general.
Meade refused Sickles' offer to withdraw because he realized it was too late and the Confederates would soon attack, putting a retreating force in even greater peril."
McPherson, James M. Battle Cry of Freedom: The Civil War Era (Oxford History of the United States). New York: Oxford University Press, 1988. Pp. 657
You will note that I said that Sickles
seemed to have realized his mistake, neither you nor I nor anyone else can possibly know what he was actually thinking in the moment, and he absolutely did offer to withdraw, an offer that Meade rejected since it was too late.