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).