The 105th Regiment Royal Garrison Artillery took over the manning of Pendennis Castle in 1902. A new barracks was built to house them, and a signal station was constructed on top of the old keep to coordinate operations with shipping, while the 16th-century guardhouse alongside the keep was demolished. The castle was reinforced by territorial soldiers during the First World War and additional defences were constructed on the landward side. It continued to defend the harbour and was also used for training purposes. After the war, Pendennis continued to be used for training gunners, but its 16th-century buildings were placed into the guardianship of the Ministry of Works in 1920, and by 1939 the fortification's artillery had all been removed.