The Southern line found itself in crisis as the Federals put heavy pressure on Hood's sector. Bragg ordered Preston's Division up as reinforcements, but Preston ordered Trigg, in the rear of his queue, to reinforce Jerome B. Robertson's Texas Brigade, of Longstreet's Corps, about a half-mile from Trigg's position. Trigg ordered an oblique right march and came to a cornfield fence where Yankee artillery again found its range. Trigg deployed his brigade along a ridge along the east Vinyard field, with the 1st Florida in front as skirmishers. Trigg's men held their fire until with they were within musket range of the 2nd Minnesota Light Artillery and its infantry support at about 2 p.m. Trigg's Brigade charged through the woods and reached the cornfield fence about 3 p.m. according to Wade, who also noted, "On reaching which a volley was fired by the brigade which drove the enemy from the cleared land in our front."

The 6th Florida got a little ahead of the brigade and was in danger from Colonel Sidney Barnes' Union Brigade of Van Clove's Division. Wade reported that the 54th closed ranks and marched abreast. Barnes' infantrymen broke and ran, but the gunners held their ground and became a rallying point for a Federal counterattack. Trigg's brigade was poised to overwhelm the Union line but Robertson felt his position was in danger. John Bell Hood, in the meantime, redirected Trigg's men to join his line which extended to the right from Trigg's position. Trigg was asked to redeploy to assist the Texans, which he agreed to do. Trigg wrote, "While thus halted and under the enemy's fire General Robertson appeared, and hurriedly informing me that his line, was very much weakened and would be beaten back unless quickly reinforced, indicated the direction in which I should move. I obliqued to the right untN I supposed that my right was opposite to his left. This brought the front of my brigade to the cornfield fence."

About this time Wilder's Lightning Brigade came up with its Spencer repeating rifles. The 6th Florida was much ahead of the rest of the brigade and took the brunt of the fire and sustained 165 casualties, more than the rest of the brigade combined for both days of battle. The Union brigades of Barnes and Cartin became entangled when Robertson and Trigg jointly struck, routing the 51 st Ohio. The 8th Kentucky (Federal) began trading fire with the Confederates and was slowly pushed back "in as good order as possible." Barnes brought up the 99th Ohio under Colonel Peter Swaine, who checked Trigg's advance. Robertson meanwhile was stubbornly fighting Carlin's Brigade. Federal reinforcements came up about 3:30 p.m., but most of Trigg's Brigade except for the 6th Florida had disengaged. The battle was over for Trigg's men on the 19th. Preston's other brigades, Grade's and Kelly's were not at all engaged on the first day, and would be rested for the 20th's fight. Trigg's brigade was not as severely cut up as many Confederate units.

There has been some speculation that the first day of Chickamauga may have been more bloody than the Battle of Sharpsburg, but this is not certain, as the battle lasted two days and it is difficult to know who was killed or wounded on which day. Though positive numbers are unknown, it would seem that the 54th sustained 3 killed and 35 wounded on September 19. Trigg's Brigade sustained 35 men killed, including 2 officers, and 130 wounded, including 11 officers, during both days of battle.

Brigadier General William Preston, in his after-action reported his situation on September 19:

...My troops remained in ranks without further reply, patiently enduring the fire. About 12 o'clock, in compliance with an order received from Major-General Buckner, I moved my command by the right flank, from about six or eight hundred yards, to a position somewhat west of north from Hunt's field. Trigg's brigade occupied the front in a woodland near a small cabin. Gracie was formed near Trigg, and Kelly was posted in the rear, supporting Leyden's... artillery.

No further event of importance occurred during the day to Gracie's or Kelly's brigades... Night coming on, Trigg bivouacked in the woodland and near the edge of the cornfield, while Gracie and Ketly occupied a position in front of a little hut, near which Major-General Buckner had established his headquarters.

September 20 dawned with no clear winner. Union troops were still on the field, despite the heavy toll in Confederate and Federal lines.

The bulk of William Preston's Division was held in reserve on the 19th by General Braxton Bragg. Only Trigg's Brigade had participated in the first day of the fight. The morning of the second day found Trigg's Brigade with the Division near the rail line leading to Atlanta and they were not called into serious action until the early afternoon. Trigg's morning assignment was to support General Manigault's Brigade. He then moved to support Williams' Artillery Battalion in the late forenoon.

William Preston's report filled in information about the situation at midday on September 20:

On Sunday, about midday, the battle became quite fierce along the right towards Chattanooga, and there was a general advance of the left wing under Lieutenant General Longstreet. Stewart's division and Trigg's brigade were moved forward northwestwardly, in the direction of Brotherton's house, on the Chattanooga road. Under an or- der from Major-General Buckner, I advanced with Grade's and Kelly's brigades, with the exception of the 65th Georgia, Colonel Moore, which was left to protect Jeffries's battery, near Hunt's field, on the left. Grade's and Kelly's brigades were formed in line of battle across the Chattanooga road in front of Brotherton's house, and Trigg a short distance in the rear. The enemy, in some fields on the north, maintained an active fire of shot and shell on my troops until about half-past three o'clock, when 1 received an order to move towards Dyer's house and field to support Brigadier General Kershaw. Guided by Captain Terrill, I advanced with Gracie's and Kelly's brigades. Trigg's having been retained near Brotherton's by Major-General Buckner to resist an apprehended attack of cavalry on our left and rear. After moving through the woodland between the Chattanooga road and Dyer's farm house, 1 reached a large field extending northward to some wooded ravines and heights.

While with Williams' artillery battalion. Trigg received an urgent message from Preston to double-quick to the support of his division, which was formed on Snodgrass Hill facing James B. Steedman's Federals. Upon Trigg's arrival the battle for the hill was raging furiously. The 54th Virginia was formed on the right of Trigg's battle line, the 6th and 7th Florida were to the left, Kelly's brigade was on their right, so the line continued uninterrupted across as much space as possible. The 1st Florida Cavalry melted into Archibald Grade's Alabama brigade on Trigg's left.

Trigg's, Kelly's and Gracie's infantry brigades, acting in rare concert, advanced together. They opened on Federal positions together and, after extremely stiff resistance, pushed Pap Thomas' Federals off the hill. Federal artillery posed a bother to Trigg's men, who ordered a bayonet charge against it, but the guns withdrew before the Southerners reached their position. After this plan fell apart, Trigg's Brigade happened upon 500 Federals, though some claim the number was 1,200. The Yankees were quickly surrounded and captured along with their much-needed small arms and accoutrements. The 54th and Trigg's Brigade were fired on by some concealed Yankees. One result was the freeing of the prisoners. Kelly reported, and his regimental commanders confirmed, that Trigg's Brigade had failed to secure its prisoners properly and allowed many of them to escape, who Kelly's men were forced to recapture at some hazard. Addison Jordan, a member of Company F of the 54th, however, reported in 1907:

At this point there were many assaults made upon the enemy by the Confederates and the attack was given up as a hopeless task. Colonel Trigg rode upon the line with his regiment against the protest of the assaulting troops and demanded surrender. The Federal officer replied: "You surrender," "I'll do nothing of the kind." said Trigg. "I have you surrounded. Fixed bayonetsl" The clicking of hammers down in the line showed the enemy was lying behind logs, and they had the drop on the 54th and could have ruined it. But the old regiment was brought up to take the guns from the enemy's hands. They captured, if I mistake not, more than double their number. This was the turn of the battle.

The culpability of the 54th Virginia in this narrowly averted fiasco is unknown. Credit for the prisoners who eventually surrendered to Colonel Trigg was divided between the 54th Virginia and the 6th Florida.

A sideline to these events created a minor sensation years after the war. The 54th claimed that its only loss during the prisoner roundup was a shot which killed Colonel Trigg's orderly. "Little Johnny" Clem of the 22nd Michigan Infantry, perhaps the youngest soldier in the Federal Army, claimed to have killed a Confederate colonel about this time and near the positions the 54th held. Clem, then aged 12, was promoted to sergeant for his action. Much research during the early years of the century and later have led to the conclusion that Clem killed Trigg's orderly and not a Confederate colonel.

William Preston wrote on October 31, 1863:

In the meantime General Buckner had sent me Colonel Trigg's brigade, which, advancing in double quick time, arrived at a critical moment, while the battle was raging fiercely. One of Trigg's regiments went to the support of General Gracie, while the remainder of the brigade was ordered to form on the left of Kelly, and to attack the enemy on the ridge. This fresh brigade, moving over the troops halted in the valley below, assaulted with great ardor the enemy on the left of Kelly, and quickly carried the ridge. The fresh and strengthened line of fire from this fine command reanimated our men, and disheartened the enemy, who relinquished their first position, and fell back to a second ridge, occupied by a strong force and behind fieldworks. A momentary lull ensued.... I sent. at this time for Colonel Kelly, who reported in person, and informed me that the enemy in his front seemed in confusion. I directed him to use his discretion and press the advantage by advancing as far as practicable, with Trigg wheeling to the right toward the declivity of the battery hill, stretching towards Chattanooga. It was now moonlight, and Kelly. returning to his command, after a few minutes absence. from It, the fire reopened, and continuing for a short time, ceased. It was the last fire of the day, and closed the battle.

Trigg's report on his activities agrees with General Preston's. Trigg wrote:

Having remained in support of this artillery [Williams' artillery battalion] until half-past two o'clock p.m., I was ordered by General Buckner to move back on the Chattano- oga road, with two of my regiments and one piece of artil- lery and select a favorable position to resist the enemy's cavalry, which it was understood had passed to our rear and was moving on that road. Whilst engaged in the discharge of this duty with the 1st Florida (dismounted) cavalry and 7th regiment Florida volunteers (Colonel Bullock) and one piece of artillery, an order from General Buckner directed me to withdraw one regiment and reJoin the division. I with- drew the 7th Florida, but had hardly put it in motion when I received from General Preston a pressing order to move rapidly to the support of the other brigades of his division [Gracie's and Kelly's],

The cavalry whose movement I had been sent to op- pose having proved to be our own, I took the responsibility of ordering the other regiment and the piece of artillery to follow, and communicated the facts to General Buckner as I passed along. The 6th Florida and 54th Virginia regiments had already been put in motion by Colonel Findley, senior Colonel. The battle was raging furiously when I arrived with the 7th Florida regiment, which I formed on the left of the 54th Virginia, which, with the 6th Florida regiment was already formed on the left of Kelly's Brigade. [The 1st Florida (dismounted) regiment, on the way to join the brigade, was detached by order of General Preston and sent to the support of General Grade's Brigade.! Without wav- ering or faltering, these two brigades-marching over some of our own troops, who were lying down-drove the enemy steadily before them, until his right was forced from its strong position, on rough, broken ground, heavily timbered. Driven from this position, he fell back upon a second line of ridges, running perpendicular to the Chattanooga road, which was already held by a strong force and protected by breastworks. When near the base of this ridge, I learned from Colonel Kelly the precise locality of the enemy, and immediately determined, with him, to attempt the capture of that part of his force in my front, my position being particularly favorable for the attainment of this end. I immediately wheeled my brigade to the right, which brought me in rear of the enemy, and moved rapidly up the hill to within twenty paces of his lines. This movement surprised him and resulted in the capture of the [22nd] Michigan, the [89th] Ohio (of Brigadier General John B. Turchin's Brigade) and part of the [21stl Ohio regiment, five stands of colors, and over [1500] small arms, of the latest and most ap- proved pattern.

The 54th suffered two killed and seven wounded on the second day at Chickamauga. The regiment's total loss amounted to 47 men either killed or wounded according to a report, but muster rolls indicate 17 killed and another 43 wounded for a total of 60 known casualties during this battle.

Colonel Trigg, commanding the 54th's brigade, commended his men after the battle when he wrote in his after-action report:

Where every officer and man did his whole duty, special mention cannot be made. The fortune of war threw the Sixth Florida regiment into the post of danger, and upon them fell the heaviest loss and proved themselves veterans in their first fight... 1 take pleasure in mentioning the following named soldiers, who have distinguished themselves by the capture, each, of a stand of enemy's colors:

Private Oscar F. Honaker, Company F, [54th]
Virginia regiment, captured the regimental flag of the [22nd]
Michigan regiment. Private W. F. Harris. Company F, [54th]
Virginia regiment, captured the State flag of the [22nd]
Michigan regiment. Private Henderson Hylton, Company A,
[54th] Virginia regiment, captured the regimental flag of the
[89th] Ohio regiment. Private Franklin Carter, Company K,
[54th] Virginia regiment, captured the State flag of the
[21st] Ohio regiment.

Trigg also credited Sergeant L. E. Timmons of the 7th Florida and Private J. H. M. Moseley of the 6th Florida with capturing stands of colors.

William Preston wrote on October 31, 1863 in his report:

The next morning I ordered the burial of the dead. Many of our brave men had fallen in charging the slope leading to the summit of the ridge. The musketry from the low breastworks of the enemy on the hill attacked by General Gracie, had set fire to the dry foliage and scorched and blackened corpses gave fearful proof of the heroism and suffering of the brave men who had stormed the hill. The ground occupied by the enemy's battery was strewn with slain.

The Confederate Army's roll of honor shows that the men of the 54th designated the following soldiers for exceptional gallantry during the battle:

Company A, Private Giles H. Roop, Killed in Action
Company B, Private Luke Cox, Mortally Wounded
Company C, Private Richard B. Haden, Mortally Wounded
Company D, Private Claibern (Clayborne) Hylton
Company E, Private Henry Griffin, Killed in Action
Company F, Corporal G. W. Chumbley
Company G, Private David W. Weddle. Killed in Action
Company H, Private Frederick Wood
Company I. Private Philip M. Walters, Killed in Action
Company K, Corporal Archibald Woods

Though the majority only saw one afternoon's fight, Preston's Division suffered tremendous losses: Grade's Brigade lost 90 killed, 576 wounded, and 2 missing for a total of 668; Kelly's Brigade lost 66 killed, 241 wounded, and 3 missing for a total of 310; and Trigg's Brigade lost 46 killed, 231 wounded, and 4 missing for a total of 281. Most of the divi- sion's 1,265 casualties were taken late on the afternoon of September 20. Trigg's Brigade's strength on September 19 was 1,417 men and 119 officers, but it was reduced to 108 officers and 1.091 men on the 20th. The total loss was more than one third of the division's strength entering the battle. General Buckner .stated: "Stewart's veterans maintained the reputation they had won on many fields. Preston's troops emulated their example and equalled them in merit. The recapitulation of the heavy losses sustained in both divisions is a sad testimony of the soldierly qualitie.s of the survivors."

Colonel Robert Trigg's performance at Chickamauga was much lauded by his superiors and General William Preston recommended Trigg's promotion to brigadier general. Preston wrote on September 28, 1863:

I recommend for promotion to your Excellency Colo. Robert C. Trigg, for gallant and meritorious conduct at the Battle of Chickamauga. At the commencement of the war Colo. Trigg raised a regiment, the 54th Va., which has been remarked for its efficiency and good discipline. Entrusted with a brigade for some time by Major General Buckner, he administered it admirably and was a month since assigned to the Division under my command. At a critical moment at the recent battle of Chickamauga, when the other two bri- gades of my Division were fiercely engaged in carrying by assault the field entrenchments and a strong position of the enemy I ordered up Colo. Trigg's Brigade from another part of the field where it was posted. By the rapidity with which the order was executed, it arrived in time and passing forward under his skillful and majestic conduct assailed the enemy with the Kelly's and Grade's Brigades drove the enemy from the field. The Brigade captured five standards, several hundred prisoners including four field officers and many valuable arms probably fifteen hundred stand.

Colo. Trigg's Brigade has an aggregate present and absent 2643 and a aggregate now present on duty of 1534. It is composed of the 1st Florida dismounted cavalry, 7th Florida, 6th Florida and 54th Virginia. Colo. Trigg has become thoroughly identified with his command, over which he exercises aleatory control. This is an attentive and excellent officer, and richly earned the permanent command of his brigade by his courage, skill and conduct at Chickamauga.