Five of these neighbourhood units (designated as fusiliers or grenadiers) made up a battalion. The castle includes the regimental museum of the Royal Welch Fusiliers. The Prince of Wales's Own Royal Regiment of Welsh Fusiliers. In May, the 6th Royal Scots Fusiliers were merged into the 15th Division. The "Fusiliers Marins" (Naval Fusiliers) and "Commandos Marine" (Naval Commandos) are naval personnel. The only original Battalion left was the 5th Royal Irish Fusiliers. This formed the 3rd and 4th Battalions of the Lancashire Fusiliers. In 1789, he was appointed colonel of the 7th Regiment of Foot (Royal Fusiliers). The castle houses the Royal Welch Fusiliers Museum. This subsequently became The Royal Fusiliers (City of London Regiment). This is a list of Northumberland Fusiliers battalions in World War I. The building is now the headquarters of the Royal Regiment of Fusiliers. Ballymullen Barracks was the depot of the Royal Munster Fusiliers. In 2006, it was renamed to the Band of the Royal Regiment of Fusiliers. He joined the British Army and was commissioned into the Royal Welch Fusiliers in 1953.