The Battle commenced at 4.20am, upon which time the artillery bombardment ceased. While the 1/4th Royal Lancasters encountered dense barbed wire, the Liverpool Irish, attacking in conditions severely limiting visibility, penetrated the front line and continued to advance rapidly. Progress had been so sudden that the first line trenches remained uncleared of German troops. The supporting 1/4th Loyals withdrew from the German trenches . Although 1st King's had entered Guillemont as well, the 1/8th was effectively unsupported after the Loyals withdrew. The battalion and its regular counterpart became isolated and surrounded. Casualties for the Liverpool Irish exceeded 550: Five officers and ten other ranks had been confirmed killed; eight officers and 47 other ranks were wounded and 502 were missing. The battle for Guillemont was renewed the following night but the village was not captured until September.

The " Great War " by H.W Wilson describes the action as follows:

The enemy by massing troops around Guillemont, close to the point of union between French and British armies, succeeded in checking the Allies advance at this point. Since July 15th when the Highlanders took Waterlot Farm, the ruins of Guillemont had been partly entered during the swaying of the battle line between Delville Wood and Trones Wood. On July 30th both the French and British attempted an advance on Guillemont but found the position too strong to be carried. The German system of works stretched southward for a mile to Falfemont Farm, on a down above Maurepas, and extended eastward for another mile to Leuze Wood and northward for another mile to Ginchy. The enemy thus had three high bases for the defence of Guillemont, which was a mass of ruins lying right at the head of the Fricourt Valley, with high ground sheltering it southward from direct fire. On August the 8th another attempt was made by Sir Douglas Haig to capture Guillemont. After the usual long and furious bombardment the British troops advanced in the darkness before dawn and broke into the village. But in the confusion and varying success of a large nocturnal operation some of the attacking forces lost touch. On the extreme right the troops did very well, and in a rapid movement conquered the high ridge south of Guillemont and gained an important stretch of ground at small cost. The forces on the left however were checked in the gloom by machine-gun fire in front of the village. This was the ordinary hazard of every trench battle where some redoubts in the hostile line have always to be enveloped. Immediately alongside the checked force another fine body of troops enjoyed better fortune and meeting with little resistance in the enemy's battered lines of work drove right into the village inflicting heavy losses on the Germans. Then occured a stroke of bad luck. The victorious troops who were still fighting amid the ruins in the darkness lost touch with the battalions held up on their left. Instead of holding on to the important part of Guillemont they had won, some of the men venturously worked through the whole chaos of brick and tumbled earth until they reached the extreme south-easten-corner of the village.
They were but a mere island in a hostile sea, with the depth of the village between them and their friends and the enemy all about them. When the sun came up and lighted the scene it was too late to rectify the lines of the operation. The German gunners swept the ground with an incessant curtain of fire, and German bombing parties continually attacked the little island of Khaki. In reply the British gunners drew their curtain of fire round the village and after a long wait to give the enveloped men a chance of fighting their way out swept all the ruins with heavy fire. In the evening some of the adventurers returned through two zones of death; the following day more came back, and in the second night and the third day others returned. Small were the numbers that fell into the hands of the enemy, though he claimed a large capture in his official report.

1917-1919: The 55th Division transferred to the Ypres Salient in October. Duties typical to trench warfare occupied the Liverpool Irish in a sector described as " quiet " before the begining of the Third Battle of Ypres on 31st July 1917. Patrols and raids were occasionally undertaken by the battalion. On the 5th June 1917, the 1/8th executed a retaliatory attack on the German trenches following a raid on the battalion that left two soldiers unaccounted for. The 2/8th Battalion arrived February and began its first tour at the front in March, in the La Bouteillerie sector. On the eve of The Third Battle of Ypres, the 55th Division was concentrated east of Wieltje. Conditions in the Ypres sector rapidly deteriorated due to the weather's volatility before the battle and the onset of sustained rains from 31st July, creating a quagmire of mud and shellholes that epitomised the offensive that became known to the Allies as Passchendale.

On the first day of ' Third Ypres ' in which 12 Allied divisions were engaged, it was intended that the Liverpool Irish would initially act as ' moppers-up ' entrusted with the responsibility of neutralising opposition on the front of the 2/5th Lancashire Fusiliers, before partial dispersal to other battalions and employment as brigade support concentrated on a line between two positions known as Keir Farm and Schuler Farm east of the village of St. Julien. The two battalions formed the left of the 164th Brigade, which was to secure the 55th Divisions third objective-the Green Line ( Gheluvelt-Langemarck Line ) after the capture of the Blue and Black lines by the

165th and 166th. Losses were sustained in the early in the advance from the battalion's trenches and steadily increased once beyond the Black Line. Various concrete emplacements and fortified positions littered that battleground, representing a constant threat with the heavy fire they directed at the brigade. Some were seized by the ' moppers-up ', at one stage the 8th's D Company took upwards of 150 prisoners.
By 12.30pm part of the Liverpool Irish had established itself on the Green Line to reinforce the severely depleted Lancashire Fusiliers in the proximity of Fokker Farm and Wurst Farm. The majority of the 1/8th concentrated near Schuler Farm. For almost 2 hours the newly captured territory was subject to sustained bombardment as a precursor to a concerted counter-attack against the Green Line, control of which was made more precarious by the exposure of the 164th's left flank. Unable to rectify the distance between it and the 118th Brigade, the contingent near Schular Farm organised a fighting retreat with those who had withdrawn from the advanced positions back to the relative security of the Black Line. The remnants of the 1/8th, approximately 163 in strength were ordered to retire to their starting positions under the command of Captain Monks.