When the Union and Confederate armies engaged near Manassas Junction, Virginia on 21 July 1861, General Jackson and his brigade earned the nickname "Stonewall" when, as they retreated to reform along Henry House Hill, Gen. Barnard Bee cried out to his ailing troops: "There stands Jackson like a stone wall. Rally behind the Virginians!" Eight of the ten companies in the 33rd were present.
At the height of the battle, it was Jackson's first brigade, and more specifically, the undersized regiment of Colonel Cummings that turned the tide of battle with a well-timed charge against an exposed artillery battery. The successful capture of the guns is thought to be largely because, due to the lack of formality in early war uniforms, Jackson's men were dressed in blue, just like their Federal counterparts. Though the 33rd Virginia succeeded in capturing the guns, the number of men that made the charge (only about 250) were unable to maintain possession and were forced to retreat. The charge had halted the steady advance of the Union Army up to that point, and precipitated further charges by Jackson's other regiments. By day's end, the actions of the 33rd led to the complete rout of the Union Army, and played a major role in immortalizing the brigade.
The cost of immortality for Cummings' regiment was high. Of the 450 men who were present at the battle, the 33rd would suffer 43 killed and 140 wounded.
Three days later, General Jackson took leave of his old brigade and returned to the Shenandoah Valley to take command of Virginia's Valley District. Finding the size of his command inadequate for the task, he petitioned Richmond for the return of the Stonewall Brigade to the Valley. On 9 November, only five days after Jackson left his command, the brigade received orders for them to pack up camp and march to Manassas Junction, where they were expected to board the train and return to the Valley.
Arriving in the evening, it was determined that there were only enough cars to take the 2nd, 5th and 27th Virginia Regiments back. The 4th and 33rd were ordered to encamp at the junction and wait for the trains to return in the morning. Around 10 o'clock, without shelter to protect them, a steady, cold rain began to fall continuing throughout the long night. Having somehow come into the possession of a barrel of whiskey, the Emerald Guard would make it longer yet and twice as miserable for the others present. "The whole of the Irish company gets drunk save a few," wrote a member of Company H, 33rd Virginia, "they get to fighting, in which swords, bayonets and knives are used; have a hard time tying them and putting them in the guardhouse. Several of both parties get badly wounded…"
News of the incident resounded all the way up to General Jackson's headquarters. On 2 December, Jackson, in his official report, provided the following account of the rowdy Irishmen. "...While the Thirty-third Regiment Virginia Volunteers was en route from Manassas to this place one of its companies (Company E) arrived in camp near here without any officer, in consequence of its first lieutenant (T.C. Fitzgerald) having absented himself without leave. In consequence of Colonel Cummings having reported to me that he could not undertake another march with the company, as it was composed of unmanageable Irishmen…"
As spring came, so did the Federals in force. Jackson, being forced to evacuated Winchester, headed southwards up the Valley until news from Jackson's cavalry scouts suggested that the Federals, were reducing their force so as to reinforce Union operations further east. Doubling back, Jackson launched an attack against the Federals situated at Kernstown a few miles south of Winchester on 23 March 1862. The 33rd played a large role in holding a stone wall against overwhelming numbers, until being ordered to retire as their ammunition became expended. The regiment suffered 23 killed, 12 wounded and 18 captured of the 275 engaged at First Kernstown.
Following Kernstown, Jackson's Army retreated down the Valley towards Rude's Hill, where, in accordance with various orders issued by the Governor of Virginia and the Confederate Congress, the existing units were reenlisted for a period of three years or the war. New recruits between the ages of 18 and 45 were encouraged through bounty and the fear of being conscripted involuntarily, to join the army. To augment recruiting, state militias were obliged to disband and its members obliged to fill up the ranks of the regular companies. By the end of April, the 33rd Virginia Infantry grew by 297 recruits and with the absorption of the militia, swelled to 762 men before breaking camp on 3 May.