The Fifth Battalion lasted from 1797-1818. It served with distinction through the whole of the Peninsular War from Roleia to Toulouse.
During the Napoleonic Wars, the King's Royal Rifle Corps saw action in the Peninsular War. The first four battalions had been raised as regular line battalions, but in 1797 a 5th battalion had been raised on Barbados, with additional companies formed on the Isle of Wight, and equipped entirely with rifles.
The troops of the Fifth Battalion were so effective that Sir Arthur Wellesley recommended their use to the divisional commanders describing them as the "most useful, active and brave troops in the field".