I stumbled upon this unsubmitted report by L.D. Sandidge, who served on Daniel Ruggles' staff. Particularly valuable for his discussion of the attack on William Tecumseh Sherman's camp on the morning of April 6. Link will be at the bottom.
On the evening prior to the battle, I encamped Ruggles' division of three brigades and four batteries of artillery and a battalion of cavalry extending Bragg's line to the left, and instead of placing the left brigade en potence with the alignment, I found that Hardee's line did not rest on Owl creek. I extended the left brigade on continuous line, its extreme left resting on Owl creek and fronting the Federal encamped advance, menacing our unprotected left flank. I finished marking the line, as directed from division headquarters, and the entire division was on the ground, before dark. The four batteries held in columns, section front, in rear of the brigade intervals; the regiments held in columns at half distance, division front — this ployment being the prescribed order; the entire line about six hundred paces in rear of Hardee's line and overlapping it, as stated, by one brigade (Ruggles'), and Withers' division on its right, forming Bragg's line, Bragg being in second line of battle; Polk's corps, composed of Breckinridge's and B. R. Johnson's brigades, in reserve to rear — B. R. Johnson's brigade leading. Such was the position, as indicated by map inclosed, on night of 4th April preceding the battle. About dark I returned from extreme left to Corinth road, rejoined you there, and we slept by slight camp-fire in the interval between Gibson's and Anderson's (Patton) brigades. In the conversation  held with you then, I asked, as you were one of the council of war, what were the leading objective points to be considered, what the plan of action, &c. You stated that after some discussion and difference of opinion in the council, General Sidney Johnston intended trying to drive the Federal left back on its centre and right, thus doubling his army against Owl creek, away from the river and gunboats. I added that was contrary to the usual plan, which was to drive the Federal forces against the broad, deep river in their rear. You replied you had stated in the council your impression “they would not swing that way” --i. e., against Owl creek-but would stubbornly fight with their gunboats at their back. My opinion then and now is, that General Sidney Johnston lost his life in a vain effort to force the Federal retreat — an army of forty-five thousand, with his one-third less — in a direction arbitrarily selected. Here I notice the point that Gibson was ignorant of the movements “above indicated placing the army in position” --a singular statement contrasted with the fact that I slept in the same apartment with him at his headquarters at Mickey's the preceding night; that the brigade and staff moved at daylight next morning in conjunction with your other troops, and in the utmost good order took position indicated, his left resting on Corinth road. From this time, say 8 P. M., every brigade and battery was ready for instant action. At daylight Sunday morning the battle began — Chalmers' skirmishers on the extreme right, in accordance with what I understood to be the plan of battle, opening fire. Instantly we were in the saddle, and you gave the first and last command I recollect your giving as a command, often repeated, and always responded to by your division: “Forward” We rode rapidly down the division line, more than a mile long, through a densely wooded, hilly country, relieved here and there only by small cultivated fields, to see that the forward movement was continuous. Before we had ridden the length of two brigades — the line moving forward all the while — after a hurried consultation with the staff, you had a gun moved in advance and threw a few shells into the heights beyond, where some of the Federals were seen moving towards Hardee's flank, to develop their design, Hardee inquiring at once into the cause of the firing. You and remaining staff continued your forward progress, while I kept down the line. By the time I returned to the right — I had ridden rapidly too — I saw the following state of affairs: Hardee withdrawn from our front, for he had in his advance gained ground  to the right so rapidly, supporting the main attack on the Federal extreme left, that very early in the morning, instead of being in second line, our division was in first line confronting Federal right-centre, not two hundred yards distant, holding elevated ground with artillery and dense masses of infantry. In my brief absence — it was not then 8 A. M.--Patton Anderson, your second brigade, had twice furiously assaulted his position, and though checked each time, had successfully reformed his brigade line amidst the smoke of the battle, and you and he were preparing to made another effort to storm the heights beyond the narrow creek separating us from the Federals. I told you you could not carry the position without more force, and inquired for your first brigade (Gibson's). You stated you had, at General Bragg's request, detached Gibson, who was following up Hardee's and Withers' advance, and were all heavily engaged on our right. I then tried to bring you forward a battalion of cavalry (Brewer's) to make a diversion obliquely from the right, proffering to lead the cavalry in person, while you were making an artillery combination to support a renewed attack. But before engaging, the cavalry made such a wide detour to the right under cover of Hardee, they were useless to us. You further directed me to ride to the rear, and if I could get no support from the reserves (Polk), I was authorized to move one of the left brigades temporarily from left to right to support Anderson's renewed attack in front. In the meantime, the left of our line was still moving forward. On going to the rear a few hundred yards, I met the head of a Tennessee regiment marching by the flank — the first regiment of B. R. Johnson's brigade, Polk's command. I saw General B. R. Johnson, told him the situation in front, and begged him to move forward to our right and assist our front attack by an oblique demonstration, which he promptly executed, being severely wounded himself at the first onset. His brigade here fired the first gun — say 10 A. M.--that was fired by Polk's command.
As soon as the head of the columns of the troops above mentioned appeared on our right, you, superintending the artillery firing (Washington artillery, &c.), again ordered “Forward I” and the indomitable Anderson a third time moved through the fire, sword in hand, and his attack, combined with the movement and attack of B. R. Johnson, finally drove the Federals--Anderson sweeping over the ground, capturing their artillery, &c. Our left brigade swung round, following up the attack, driving the Federals  back towards the river — we, in truth, being more successful than the main attack made from our right. In a word, the Federals declined to drive from the river at all, as you predicted in the council. The Federals, though driven from our front, moved rearward very slowly, contesting every inch. After we got them started, I again rode down the left of our line, directing our left brigade forward. The Federal right about this time began to swing rearward much faster than his right-centre, and it was evident they were falling back to concentrate on and strengthen the Federal centre and left, so heavily assaulted all the morning by the main effort to cut them off from the river. On my return to the extreme right of our division line, about noon, I found you had continued to drive the Federal right-centre to a certain point in an old field, where they were making a determined stand. I noticed here a long gap between our line and where I supposed Withers' left ought to be, and called your attention. We then thought it dangerous to leave it open, as a failure on our right and a furious effort on the part of the Federals in our front, if we failed to check, would imperil our rear. You directed me to fill up the interval with any detached infantry I could find, and at once bring forward all the artillery I could get to move, and have them open fire at once on the Federals in front, to prevent their making any movement endangering our position, and keep them moving in retreat. It was here that we finally, in a few hours, got between fifty and sixty field guns in position, and under this heavy fire you succeeded in moving again the Federals in our front, who had held their position so long and obstinately that when they started they found troops of Hardee and Withers on their left and rear, and our left brigade and the head of Polk's reserves on their right and rear, intercepting their march. A portion of Polk's column following the onward march of our left, both swinging to the right as they [moved forward, found themselves simultaneously on the rear and right of the Federal position. Here being assaulted in front by you with infantry and artillery, as stated, and hemmed in, 2,500 with Prentiss surrendered. It was at the point above mentioned, when we were getting this artillery together, I first heard of General Sidney Johnston's death on our right.
The Federals by this time were concentrating along the river front all their remaining artillery and every infantry organization that could hold together, and were fighting for existence. The advance and attack continued--General Bragg issuing orders to  bring everything forward, and in less than an hour after Prentiss laid down his arms we rode over the ground his brigade stood in our advance. But now Leu Wallace was on our flank with 10,000 fresh troops from Pittsburg Landing. Nelson, leading Buel's army, 25,000 strong, was crossing the river in our front, and we were beginning to feel his fire. But an half hour of sun remained. It was impossible — though more than one assault was made to drive the defeated Federals into the river — to do anything more without reorganizing our troops, which was done during the night; but on the morrow the new army had to be fought on the same field. How that was done let history tell. I am certain I saw General Beauregard leading Mouton's regiment of our brigade in person, when you and Mouton, with the entire line, attacked the enemy's centre, and again two more of the brigades (Anderson's and Pond's) prolonged on the line of Cheatham at Shiloh church, again and again advanced by successive alignments, you and staff carrying the battle flags, repelling every attack of the fresh army of Monday (see Basil Duke's Forrest's Cavalry — foot note on Shiloh), till the Confederate army, moving in regular order, retired leisurely by the passage of lines from the field towards Corinth. Breckinridge and his Kentuckians will remember when their brigade was left on the field, interposed to secure retreat, a staff officer came through the rain and mire with General Ruggles' compliments and message that not one Louisianian would move a pace in retreat at the peril of a life in the brigade — the entire division to reinforce him — and his answer, “Sandidge, go tell you Louisianians God bless them! If they hear not our guns at dawn of the morning, send back a flag that we may have honorable burial, for we are enough to die!”