A pre-war shipping map shows why the theatre mattered even when its battles received less attention than those in the Atlantic or Pacific. A dense route connected Britain to Suez, the Red Sea, India, and Southeast Asia, while another ran down the west coast of Africa. Once Italy entered the war, traffic diverted around the Cape as troop and supply movements for North Africa, the eastern Mediterranean, and East Africa added to the burden. The result was a maritime system whose weak points could affect campaigns far beyond the ocean itself. German, Italian, and Japanese submarines would make protection of these routes resemble the Battle of the Atlantic on another immense ocean.
Chapter · 5:52-9:27
The sea lanes that made the Indian Ocean strategic
British and Dominion trade moved through Suez, the Red Sea, India, and Southeast Asia, making the ocean both a vital supply route and a second theatre of commerce warfare.