This is Sickles' version of the events of July 2, directly extracted from his March 1864 testimony before the Joint Committee on the Conduct of the War. It's quite amusing, and some brilliant political spin doctoring:
At a very early hour on Thursday morning I received a notification that General Meade's headquarters had been established at Gettysburg, and I was directed by him to relieve a division of the 12th corps, (General Geary's division, I think,) which was massed a little to my left, and which had taken position there during the night. I did so, reporting, however, to General Meade that that division was not in position, but was merely massed in my vicinity; the tenor of his order seemed to indicate a supposition on his part that the division was in position. I also received a notification from General Meade that he approved of my course in moving up to Gettysburg. Of course, as soon as I had determined to do that, I addressed a communication to General Meade from Emmettsburg, informing him of what I had done, and expressing my anxiety to have his sanction of it. I received a communication from him informing me that he approved of my course, and that the two brigades and two batteries which I had left at Emmettsburg would be relieved and ordered to join me. I brought them up during the night, under General Graham, and they arrived in the neighborhood of daybreak. Not having received any orders in reference to my position, and observing, from the enemy's movements on our left, what I thought to be conclusive indications of a design on their part to attack there, and that seeming to me to be our most assailable point, I went in person to headquarters and reported the facts and circumstances which led me to believe that an attack would be made there, and asked for orders. I did not receive any orders, and I found that my impression as to the intention of the enemy to attack in that direction was not concurred in at headquarters; and I was satisfied, from information which I received, that it was intended to retreat from Gettysburg. I asked General Meade to go over the ground on the left and examine it. He said his engagements did not permit him to do that. I then asked him to send General Warren with me, or by himself; but General Warren's engagements were such as to make it inconvenient for him to go. I then asked him to send General Hunt, his chief of artillery, and that was done. General Hunt accompanied me upon a careful reconnoissance of the whole position on the left, in reference to its topography and the best line for us to occupy, and also with reference to the movements of the enemy. I pointed out to General Hunt the line that on a subsequent part of the day, when the battle opened, I actually occupied; that is, a line from Round Top on the left, perpendicular to the Emmettsburg road, but somewhat en echelon, with the line of battle established on Cemetery ridge. I asked for General Hunt's sanction, in the name of General Meade, for the occupation of that line. He declined to give it, although he said it met with the approval of his own judgment; but he said that I would undoubtedly receive such orders as soon as he reported to General Meade. Before making my dispositions on that line, I waited for some time for orders, but received none. The enemy's demonstrations became more and more decided.
I had strengthened and supported my outposts in order to give me timely notice of the attack, which I knew was very imminent. Buford's cavalry, which had been on the left, had been withdrawn. I remonstrated against that, and expressed the hope that the cavalry, or some portion of it, at all events, might be allowed to remain there. I was informed that it was not the intention to remove the whole of the cavalry, and that a portion of it would be returned. It did not return, however.
My outposts became engaged, and were being driven back from their supports. I determined to wait no longer the absence of orders, and proceeded to make my dispositions on the advanced line, as it is called. I took up that position, which is described in the report of General Halleck as a line from half to three-quarters of a mile in advance, as he says, and which, in his report, he very pointedly disapproves of, and which he further says I took up through a misinterpretation of orders. It was not through any misinterpretation of orders. It was either a good line or a bad one, and, whichever it was, I took it on my own responsibility, except so far as I have already stated, that it was approved of in general terms by General Hunt, of General Meade's staff, who accompanied me in the examination of it. I took up that line because it enabled me to hold commanding ground, which, if the enemy had been allowed to take — as they would have taken it if I had not occupied it in force — would have rendered our position on the left untenable; and, in my judgment, would have turned the fortunes of the day hopelessly against us. I think that any general who would look at the topography of the country there would naturally come to the same conclusion.
While I was making my dispositions on this line I received communication from headquarters to attend a consultation of corps commanders. I sent word verbally by the officer who brought me the communication, begging, if possible, to be excused, stating that the enemy were in great force in my front, and intimating that I would very soon be engaged, and that I was making my dispositions to meet the attack. I hastened forward the movements of my troops as rapidly as possible, and had got my batteries in position, when I received another and peremptory order to report at once in person at headquarters, to meet the corps commanders. I turned over the command temporarily to General Birney in my absence, feeling assured that before I could return the engagement would open. I hastened to headquarters with all speed, but before I got there the sound of the cannon announced that the battle had opened. However, I was quite near headquarters at the time and pushed on, but found that the consultation had been broken up by the opening of the battle. General Meade met me just outside of his headquarters and excused me from dismounting. He remarked that he observed, from the sound of the cannon, that my troops were engaged with the enemy. He said that I should return at once, and that he would follow me very soon.
On my way I found that the enemy were moving up to the attack in great force, in two lines of battle, supported by three columns. Fortunately, my left had succeeded in getting into position on Round Top and along the commanding ridge to which I have referred; and those positions were firmly held by the 3d corps. General Meade soon afterwards arrived on the field and made a rapid examination of the dispositions which I had made, and of the situation. He remarked to me that my line was too extended, and expressed his doubts as to my being able to hold so extended a line, in which I coincided in the main — that is to say, I replied that I could not, with one corps, hold so extended a line against the rebel army; but that, if supported, the line could be held; and, in my judgment, it was a strong line, and the best one. I stated, however, that if he disapproved of it it was not yet too late to take any position he might indicate. He said “No;” that it would be better to hold that line, and he would send up the 5th corps to support me. I expressed my belief in my ability to hold that line until supports could arrive. He said he would send up the 5th corps on my left, and that on my right I could look to General Hancock for support of my right flank. I added that I should want considerable artillery; that the enemy were developing a strong force of artillery. He authorized me to send to General Hunt, who commanded the reserve of the artillery, for as much artillery as I wanted. I then assured him of my entire confidence in my ability to hold the position; which I did. The 5th corps came up, somewhat tardily, to be sure. It was three-quarters of an hour, or an hour, I suppose, before it got into position. My request to General Hancock for supports was promptly met; and I feel myself under obligations principally to General Hancock and the troops of his command for the effective support which enabled me, in connection with my own corps and the artillery which I received from the reserve, to hold the position during that very desperate encounter of Thursday, where the principal operations of Thursday occurred. The position was held, and the attacks of the enemy, which were made in great force and with great obstinacy and determination, were successfully repulsed, with terrific loss to them and a very heavy loss on our side, until I was wounded and carried from the field. The command of the 3d corps then devolved on Major General Birney, and, of course, I only know about the subsequent operations from the perusal of his report.