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.

Surabaya is the capital city of East Java province and the second-largest city in Indonesia, after Jakarta. Located on the northeastern corner of Java island, on the Madura Strait, it is one of the earliest port cities in Southeast Asia. According to the National Development Planning Agency, Surabaya is one of the four main central cities of Indonesia, alongside Jakarta, Medan, and Makassar. The city had a population of 2,874,314 within its city limits at the 2020 census. With 3,009,286 people living in the city as of mid 2023 and over 10 million in the extended Surabaya metropolitan area, according to the latest official estimate, Surabaya is the second-largest metropolitan area in Indonesia. Surabaya metropolitan is also ASEAN's 6th largest economy ahead of Hanoi. In 2023, the city's GRP PPP was estimated at US$150.294 billion.

Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania, between the Indian and Pacific oceans. Comprising over 17,000 islands, including Sumatra, Java, Sulawesi, and parts of Borneo and New Guinea, Indonesia is the world's largest archipelagic state and the 14th-largest country by area, at 1,904,569 square kilometres. With over 280 million people, Indonesia is the world's fourth-most-populous country and the most populous Muslim-majority country. Java, the world's most populous island, is home to more than half of the country's population.