Heavy fighting in Surabaya between Indonesian nationalists and returning colonialists after World War II, today celebrated as Heroes' Day (Hari Pahlawan).

The Battle of Surabaya was a major battle in the Indonesian National Revolution fought between regular infantry and militia of the Indonesian nationalist movement and British and British Indian troops against the re-imposition of Dutch colonial rule. The peak of the battle was in November 1945, and was the largest 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.