About 200 Irish Guards marched through the centre of Liverpool to mark its strong links to the city.
The regiment was given the freedom of Liverpool in 2000
The regiment's 1st Battalion, which has just returned from a tour of duty in Iraq, were joined by army cadets during the parade on Saturday morning.
The troops attended a special service at the Anglican cathedral before parading down Lime Street to St John's memorial gardens.
A new memorial to fallen comrades was then unveiled in the gardens.
Many of the regiment's original recruits, when it was formed in 1900, came from Irishmen living in Liverpool.
It was given the freedom of Liverpool to mark its centenary in 2000.
Michael Hogan, 37, and his two brothers James, 32, and Peter, 26, all of Netherley, Liverpool, who serve in the 1st Battalion, took part in the parade.