High Quality Content by WIKIPEDIA articles! The Battle of Surabaya was fought between pro-Independence Indonesian soldiers and militia against British and Dutch troops as a part of the Indonesian National Revolution. The peak of the battle was in November 1945. Despite fierce resistance, British and Indian troops managed to conquer Surabaya, the second largest city in Indonesia, on behalf of the Netherlands. The Battle was the heaviest single battle of the Revolution and became a national symbol of Indonesian resistance. Considered a heroic effort by Indonesians, the battle helped galvanise Indonesian and international support for Indonesian independence. 10 November is celebrated annually as Heroes' Day (Hari Pahlawan). By the time the Allied forces arrived at the end of October 1945, the pemuda ('youth') foothold in Surabaya city was described as "a strong unified fortress". Ferocious fighting erupted when 6,000 Indian troops landed in the city to evacuate European internees. Following the killing of the British officer Brigadier Mallaby on 30 October, the British retaliated with a punitive sweep beginning on 10 November under the cover of air attacks.