It seems that actual orders for Pickett to begin his advance were never uttered. It is reported that Longstreet was so reluctant to assume responsibility for the attack that he saw as futile, that he attempted to hand-off the responsibility of initiating the attack to COL Alexander. Since Alexander had been ‘anointed’ by Lee as commanding the barrage, Longstreet saw fit to tell him to tell Pickett when the objective had been achieved. Naturally, Alexander faltered at this action. Over the course of the hour-long bombardment, he exchanged messages with Longstreet as to when the infantry should move.
Finally, as the rate of fire of the cannons diminished as ammo ran low, Pickett approached Longstreet for permission to advance. Longstreet’s reply — rather than a firm order — was only a nod of his head.
And so the slaughter began……