By the time British forces arrived at the end of October 1945, the Pemuda ("youth") foothold in Surabaya City was described as "a strong unified fortress".

Although the colonial forces largely captured the city in three days, the poorly armed Republicans fought for three weeks, and thousands died as the population fled to the countryside.

As the news about the independence declaration spread throughout the archipelago, ordinary Indonesians felt a sense of freedom that led most to regard themselves as pro-Republican.

[8] The senior Japanese commander in Surabaya, Vice Admiral Shibata Yaichiro, threw his support behind the Republicans and gave Indonesians ready access to arms.

In the meantime, British commanders had become preoccupied with the increasing boldness and apparent strength of the nationalists, who attacked demoralised Japanese garrisons across the archipelago with rudimentary weapons such as bamboo spears to seize their arms.

In September and October 1945 a series of incidents took place involving pro-Dutch Eurasians, and atrocities were committed by Indonesian mobs against European internees.

[2][12] On 26 October 1945, Brigadier A. W. S. Mallaby reached an agreement with Suryo, the Republic of Indonesia's governor of East Java, that the British would not ask Indonesian troops or militia to hand over their weapons.

[5] On 27 October 1945, a British plane from Jakarta dropped leaflets over Surabaya urging all Indonesian troops and militia to surrender their weapons.

A ceasefire was negotiated with Major General Hawthorn (the commander of the 23rd British Indian Division) and Brigadier Mallaby and immediately adhered to.

Later while patrolling, they received information that there was a mass of Indonesian militia advancing to the International Bank near Jembatan Merah (the "Red Bridge").

When his car approached the British troops' post in the International building near the Jembatan Merah, it was surrounded by Indonesian Republican militia.

[5] Captain R. C. Smith, who was in the stationary car, reported that a young Republican (teen) suddenly shot and killed Mallaby after a short conversation.

The Indonesians rejected the ultimatum and many figures encouraged the civilians to resist the British, including Bung Tomo via radio broadcasts.

[14] Indonesian irregulars would continue to infiltrate the city to launch guerilla attacks and the British forces would bombard Surabaya until 2 December.

[2] The battle for Surabaya was the bloodiest single engagement of the war, and demonstrated the determination of the rag-tag nationalist forces; their sacrificial resistance became a symbol and rallying cry for the revolution.

It also made the British reluctant to be sucked into a war, considering how stretched their resources in southeast Asia were during the period after the Japanese surrender; within a few years, in fact, Britain openly supported the Republican cause in the United Nations.

[19] The Scottish-American Indonesian sympathiser K'tut Tantri also witnessed the Battle of Surabaya, which she later recorded in her memoirs Revolt in Paradise.

Following the British bombardment of the city, Tantri contacted several foreign diplomats and commercial attaches from Denmark, Switzerland, the Soviet Union, and Sweden.