Bit of an update and further thoughts... I've finished
Maps of Chickamauga and have started on
Mad Irregular Battle. Very much enjoying the writing and scholarship and learning about a battle that's always been rather mysterious to me.
In the realm of retracing the course of my great-great-grandfather's unit, I think I have a decent basic knowledge of how it went. The 14th OVI (part of Croxton's brigade, Brannan's division, Thomas's XIV Corps, and a relatively large formation for a regiment in that phase of the war, due to their having missed action at a number of places for one reason or another) comes "onstage" as it were north of Winfrey Field in the midmorning of September 19, opposing Forrest and the formations supporting him. They were then pulled back a little way along Alexander's Bridge Road for a respite, before being shifted south of the road and going into action again just west of the crossroads of Alexander's Bridge and Brotherton Roads. They were then pulled out again up Alexander's Bridge Road for rest and resupply, a bit southeast of McDonald Field, before being placed in line just north of Poe Field for the evening.
On the 20th, the 14th was just north of Poe Field in the second line of the double line of regiments in the formation Croxton had formed his brigade, and held briefly before being pushed back and partly overrun when Longstreet smashed into the Union center. Portions of the 14th were in the scratch formation that Croxton (and then Hays) pulled together that defended Hill 2 of Horseshoe Ridge for the afternoon. So there were four distinct contact points, two on the 19th and two on the 20th, that should be locateable. I don't know how practical/possible it is to literally retrace the walking course, but I can probably visit those individual sites in sequence.
(During this battle, the 14th, which began with a force of 449, suffered 245 casualties-- about half of those being wounded.)
Incidentally, the 14th's original colonel was James B. "Make sure they spell my name right" Steedman, although by the time of Chickamauga he was commanding a division of Granger's Reserve Corps.
With reference to the OP question, it seems clear that Rosecrans' goal was no less than defeating Bragg's entire army southeast of Chattanooga, and they were swinging wide to trap him-- and, thanks to poor cavalry support by Wheeler and Forrest, Rosey came perilously close to pulling it off. The terrain seems to have played a significant role in making the entrapment more difficult than anticipated, scattering the Union elements over a wide area; Bragg began concentrating first, but again through poor intelligence missed his chance to defeat the Army of the Cumberland in detail. So, in essence, the Union goal was the entrapment and destruction of the Army of Tennessee, and they did not accomplish that.
The 14th's commander made this report about the actions at Chickamauga (when Kingsbury says they were "on the right," he means on the right side of the brigade):
HDQRS. FOURTEENTH OHIO VOLUNTEER INFANTRY,
Chattanooga, Tenn.,
September 26, 1863.
CAPT.:
I have the honor to submit the following as a report of the part taken during the two days' engagement with the enemy by my command:
The morning of the 19th, before any firing was commenced, after moving in line, my command occupied the right of the second line, in rear of the Tenth Indiana, consisting of 18 commissioned officers and 442 enlisted men.
In this position we advanced 500 yards when we were ordered to the extreme right of the front line, where skirmishers were thrown out covering our front.
A heavy force of infantry were seen approaching our extreme right, and the Seventy-fourth Indiana were formed upon our right to meet them. The enemy advanced with three colums of infantry, without skirmishers, and forced us to retire.
In the afternoon, when the advance was again made more to the right, our position was still on the extreme right.
In this position we were ordered to [move] forward until we came to an open field or the left of the line should halt. In this position we advanced about 200 yards, when the enemy's skirmishers were met and driven back. We then charged upon their line and drove them for over 200 yards, when our line met a superior force and, being outflanked, retired fighting. We were then moved to the right, but without any more fighting. We lay in an open field near where the brigade was halted for breakfast till 6.30 p. m., when we were ordered to the rear for the night. Our loss during the day was 29 killed, 7 commissioned officers and 130 enlisted men wounded, and 31 reported missing.
At 3 o'clock the morning of the 20th we moved by the right flank to the right of the road, and took position in the second line, in rear of the Thirty-first Ohio and a battery, and on the right of the Tenth Kentucky.
We were in this position when the line on our right was turned, and held the position until the right was so far driven back that the enemy held position in our rear, and were forced to retire. We fell back across the field, and there rallied what men I could and formed them upon the hill. During the confusion my command became separated and were kept so during the day; but from what fell under my own observation I can report that I never saw men, disorganized as they were, fight better.
The major and several other of the officers, with what men they could rally, remained upon the hill to the right of the hospital (on the right), and fought until the enemy fell back and gave up the contest. It was 6.30 p. m. when they were withdrawn and moved to the rear.
The confusion which we were at times thrown into renders a more explicit report impracticable. Our colors were shot down three times on the 19th and twice on the 20th, but were bravely defended and brought from the field at night.
The loss on the 20th was 7 men killed, 1 commissioned officer and 29 men wounded, and 12 missing.
I am, captain, very respectfully, your obedient servant,
H. D. KINGSBURY,
Lieut.-Col., Comdg.
Capt. LOUIS J. LAMBERT, Asst. Adjt. Gen., Third Div., 14th Army Corps.