It's surprising that so little has been written (here or anywhere) about one of the most powerful songs made during the Civil War.

Its earliest printed appearance was in Francis D. Allan, ed., "Allan's Lone Star Ballads: A Collection of Southern Patriotic Songs Made During Confederate Times" (Galveston: Sawyer, 1874):

                                  THE BATTLE OF SHILOH HILL.

    BY M. B. SMITH, OF CO. C, SECOND REGIMENT TEXAS VOLUNTEERS.

                                  Air— Wandering Sailor.

Come all you valiant soldiers, and a story I will tell,
It is of a noted battle you all remember well;
It was an awful strife, and will cause your blood to chill,
It was the famous battle that was fought on Shiloh Hill!

It was the sixth of April, just at the break of day,
The drums and fifes were playing for us to march away;
The feeling of that hour I do remember still,
For the wounded and the dying that lay on Shiloh Hill.

About the hour of sunrise the battle it began,
And before the (lay had vanished we fought them hand to hand;
The horrors of the field did my heart with anguish fill,
For the wounded and the dying that lay ou Shiloh Hill.

There were men of ev'ry nation laid on those bloody plains.
Fathers, sons, and brothers were numbered, with the slain,
That has caus'd so many homes with deep mourning to be fill'd,
All from the bloody battle that was fought on Shiloh Hill.

The wounded men were crying for help from everywhere,
While others, who were dying, were offering God their prayer,
'Protect my wife and children, if it is thy holy will!"
Such were the prayers I heard that night on Shiloh Hill.

And early the next morning, we were call'd to arms again,
Unmindful of the wounded and unmindful of the slain,
The struggle was renewed, and ten thousand men were kill'd;
This was the second conflict of the famous Shiloh Hill.

The battle it raged on, though dead and dying men
Lay thick all o'er the ground, on the hill and on the glen,
And from their deadly wounds their blood ran like a rill;
Such were the mournful sights that I saw on Shiloh Hill.

Before the day was ended the battle ceased to roar,   
And thousands of brave soldiers had fell to rise no more;
They left their vacant ranks for some other ones to fill,
And now their mouldering bodies all lie on Shiloh Hill.

And now my song is ended about those bloody plains,
I hope the sight by mortal man may ne'er be seen again;
But I pray to God, the Saviour, "if consistent with thy will,
To save the souls of all who fell on bloody Shiloh Hill!"

A very similar text is printed in the St. John's Review (Portland, Ore.) (June 19, 1914). It was attributed to "J.T. Holley 9th Missouri Cavalry and 18th Illinois Infantry."

The lyrics reappeared anonymously in the Weekly Thibodaux (La.) Sentinel (Aug. 2, 1879), but the air is given as “The Watcher.’

An Ozark version, clearly derived from the above, appeared in Vance Randolph's "Ozark Folk Songs." The song was made familiar to the “revival” through appearing in Irwin Silber’s “Songs of the Civil War” (1960) and Alan Lomax’s “Folk Songs of North America” (1965).

The Pickens (S.C.) Sentinel printed another very similar text on April 15, 1915. Its chief distinction is a division into quatrains, with a chorus of “Sing carry me away,/ Oh, carry me away.” The text is introduced with the following note:

      “Mr. Editor: Will you please pint this song in memory of my dear father,
       Joe Berry Rigdon, who left this world November. 26, 1911, and who
       dearly loved it? I have heard him talk about the battle of Shiloh many
       times. [Signed] Mrs. Nannie Rigdon Massengill.”

In the Iron County (Mo.) Register (June 2, 1910), a Mr. F. Hilburn mentioned “On the Top of Shiloh Hill” as among the songs he sang in his youth.

The text in the DT radically adds a melodramatic scene in which the narrator (a Union soldier) unwittingly kills his Confederate father in battle, is from West Virginia. Alice Wylde sings it on “Songs of Old Appalachia” (2013).

“Allan’s Lone Star Ballads” includes several other lyrics credited to M. B.Smith: “The Land of Texas,” “The Glorious January 1, 1863,” “Hard Times!” “The Lone Texas Star,” “The Gallant Second Texians,” and “The Frontier Ranger.”

I have found no further information on M. B. Smith except that he lived in or near Galveston after the war. I don’t know whether he was an officer or an enlisted man in the Second Texas. “The Frontier Ranger” suggests the possibility that he once belonged to the Texas Rangers. (No information on J. T. Holley seems to be available either.) If Smith was the author of “Shiloh Hill,” his view of the battle in “The Gallant Second Texians” was more conventional:

       'Twas at the Shiloh battle they first did hear the cry,
       The cannons loudly rattle, and bullets rattle by—
       They rush'd forth like lions' whelps upon the dastard foe;
       Away, o'er dead and dying, behold them onward go!