After a request to The Union Defence Force (UDF) Headquarters, authority was granted to form the regiment and Lieutenant-Colonel Brennan was appointed as its first commanding officer.

The wife of General Louis Botha (a lady of Irish descent with the maiden name of Emmett) was appointed as the regiment's first honorary colonel.

At the end of the campaign in South-West Africa, Active Citizen Force regiments were by law not permitted to proceed to other theatres of war as such.

In July of the same year, the brigade was shipped to Kenya via the port of Durban to become part of 1st South African Infantry Division.

5 South African Infantry Brigade, together with the Transvaal Horse Artillery Regiment, took part in the fighting at Sidi Rezegh culminating on 23 November 1941 with the German armour overwhelming the Allied forces, destroying 5 Brigade, and breaking through to the Eighth Army's rear areas on the Libyan border with Egypt.

The casualties of the South African Irish were extremely heavy (only 140 men of all ranks survived), including its commanding officer, Lieutenant-Colonel Dobbs who was wounded in the early stages of the battle (he was replaced by Major C. McN.

The survivors of the regiment served with New Zealand forces until the end of November when they rejoined the remnants of the decimated Brigade at Mersa Matruh.

Due to their heavy losses, the South African Irish and 3 Transvaal Scottish ceased to exist as independent infantry units.

2nd Regiment Botha was then further reinforced with replacements coming from the 2nd Witwatersrand Rifles after which, the battalion moved by rail and in New Zealand troop carriers from Mersa Matruh to El Adem.

This unit later returned to North Africa as a component of the South African 6th Armoured Division and also took part in the subsequent fighting in Italy.

However, as there was no intention at that time to establish additional Active Citizen Force infantry battalions, this request was refused.

The period from 1974 to 1988 saw the regiment being part of 7th South African Infantry Division's 72nd Motorised Brigade and being re-established as a conventional force.

In 1979 the regiment was granted the Freedom of entry to the City of Barberton because of the WWII training period and the frequent "raids" to the town.

During this period the regiment successfully completed township unrest camps as well as training exercises at the Army Battle School.

From 1992 to 1998 the regiment went through a period of significant decline as the annual intake of national servicemen dried up with the ending of conscription.

In August 2019, 52 Reserve Force units had their names changed to reflect the diverse military history of South Africa.

The motto echoes the history of the Royal Irish Fusiliers the First Battalion of which was known as the 'Faugh-a-Ballaghs', an honorary title conferred upon them during the Peninsular War (1809–1812).