After the Great War the regiments reverted to their pre-war establishment. Only the Welsh Guards were an addition.
In 1920/21 many regiments changed their title, often exchanging the primary and secondary part of it.
On the creation of the Irish Free State in 1922, twenty-three battalions where disbanded. Five two battalion regiments, three second battalions and five pairs of 3rd and 4th battalions.
In 1935 some regiments were made "Royal" because of their service in the Great War.