During WW1 the docks came under Military control. All British merchant ships were requisitioned and delivery of coal to the Royal Navy was prioritised.
Neale and West trawlers and P & A Campbell paddle steamers were taken over for mine-sweeping. German U-boats aimed to blockade the U.K. During the conflict 205 Cardiff registered or owned ships were lost to U-boats as together with another 128 that had sailed from Cardiff. At least 1500 seamen, who had come mainly from British Empire countries, were lost.
After USA entered war in 1917 a naval HQ was set up at Angel Hotel which was known as USS Chatinouka.
In WW2 the docks came under the control of Ministry of War Transport and was used as a supply base and so became the target for Luftwaffe air raids especially in early 1941.
The paddle steamers were again requisitioned as mine-sweepers but some were also involved in the evacuation from Dunkirk in 1940
From 1942 enormous quantities of USA military supplies and personnel flowed through the docks especially in preparation for the Normandy D-day landings and subsequent operations.
