"Dorsetshire" was berthed at the naval base at Simon's Town, South Africa, on 7 December 1941 when the Japanese attacked Pearl Harbor and, soon after, British positions at Hong Kong, Shanghai and Malaya. She was immediately assigned to escort a convoy of British troops just arriving from Halifax in American transports, originally destined for the Middle East, but now diverted to Singapore. She guided them to Bombay and then returned to Durban to escort another convoy to Aden and Bombay. This was essential duty as these convoys were now vulnerable to attack by both German and Japanese raiders, passing by the less than friendly Vichy French island of Madagascar. "Dorsetshire" then was assigned to escort a convoy to withdraw as many civilians from Singapore as possible before the island was overrun by the Japanese. She got them safely to Colombo, Ceylon.