The outbreak of the Second World War in September 1939 immediately ended "Walmer Castle"s liner service to and from Germany. At first Union-Castle chartered her to companies that specialised in short-sea cargo trade. She traded with French ports first in the Bay of Biscay and later in the English Channel. After France capitulated in June 1940 "Walmer Castle" carried cement to UK ports to build fortifications against the threat of invasion.