In 1915, it was decided to reactivate HMS "Thistle" and transfer her to East Africa. The initial intention was to send her into the Rufiji Delta to fight the German cruiser SMS "Königsberg", but the Admiralty modified its plans by also sending the monitors HMS "Mersey" and HMS "Severn" through the Suez Canal, and they subsequently destroyed the "Königsberg" before the "Thistle" even set sail.