It was formed on 1 July 1999 following the Strategic Defence Review by the amalgamation of the 4th (Volunteer) Battalion, Queen's Lancashire Regiment and the 4th (Volunteer) Battalion, King's Own Royal Border Regiment.

On 1 July 2006,[1] the regiment was re-designated as the 4th Battalion, Duke of Lancaster's Regiment (King's, Lancashire and Border).

This initial structure of the regiment, upon creation, was as follows:[2] Three months prior to re-designation as a battalion of the Duke of Lancaster's Regiment, the King's Regiment companies of the King's and Cheshire Regiment were integrated into the structure of the regiment, in order to ease the process of re-designation.

[2] In July 2006, as part of Delivering Security in a Changing World, the regiment was transferred to the Duke of Lancaster's Regiment, and designated as the 4th Battalion.

It now acts as the reserve infantry battalion for Merseyside, Lancashire, Greater Manchester, and Cumbria, with sub-units dispersed throughout all four counties.