OXFORD, England — Two and a half million soldiers drawn from Britain’s empire in South Asia fought in World War II. But they are missing from many British commemorations and accounts of the war — an absence reinforced by Christopher Nolan’s new film “Dunkirk,” which does not feature any of the Indian soldiers who were present at the battle.The Indian soldiers at Dunkirk were mainly Muslims from areas of British India that later became Pakistan. They were part of the Royal India Army Service Corps — transport companies that sailed from Bombay to Marseille. The men brought with them hundreds of mules, requested by the Allies in France because of the shortage of other means of transport. They played a significant role, ferrying equipment and supplies.The Germans captured one Indian company and held the men as prisoners of war. Others were evacuated and made it to Britain. Paddy Ashdown, a British politician, has spoken of his father’s being court-martialed for refusing orders to abandon the Indian troops under his command.