Revealed: the day war came to Sydney

In 1942 the world was at war but Sydney, despite the fall of Singapore and the bombing of Darwin, felt immune. That complacency was shattered on 31 May when three Japanese midget submarines sneaked into Sydney Harbour and sank a ferry, killing 21 sailors.

In 1942 the world was at war but Sydney, despite the fall of Singapore and the bombing of Darwin, felt immune. That complacency was shattered on 31 May when three Japanese midget submarines sneaked into Sydney Harbour and sank a ferry, killing 21 sailors.

The daring assault sparked fears of a Japanese invasion, and many residents sold up and fled to the Blue Mountains. But while the incident marked a turning-point for Australia, the events of that night have always been clouded by myth and rumour.

A documentary to be shown at the Sydney Film Festival this month attempts to set the record straight. Sydney at War - The Untold Story interweaves old footage with interviews with survivors, casting new light on an incident that shook the city out of its apathy.

The mission was an unsuccessful bid to divert Allied naval power from the decisive battle fought near Midway, in the Pacific, a week later. The submarines, part of a taskforce assembled to attack ships in enemy ports, were launched from a "mother" submarine 35 miles east of Sydney Heads.

Warrant Flying Officer Susumu Ito, who conducted a reconnaissance flight, told the film's director, Claude Gonzalez: "We knew little about Australia, except a few things, like it had a White Australia policy that did not allow migrants of coloured races ... the land was populated only on the east coast, the rest was virtually a desert."

As his seaplane flew low over the harbour, he observed that fully lit merchant ships were moving around and lights were on at the airport. "It was clear that Sydney was not on alert," he said. "It was a carefree atmosphere."

At midnight the next day, the midget subs were dispatched, each crewed by two young men. All six knew they were heading for certain death. "The last day of my life arrived belatedly today," Petty Officer Masao Tsuzuku wrote to his two sisters before setting off. As Mr Ito said: "It was heart-rending for those of us who sent them. We knew it was for the sake of our country, but we wished they would somehow manage to come back alive."

After entering the harbour, the mini-subs were trapped in torpedo nets. Bombarded by depth charges, Tsuzuku and his commanding officer, Lieutenant Keiu Matsuo, shot themselves. The occupants of a second sub were also found dead.

In the third were Petty Officer Mamoru Ashibe and Sub-Lieutenant Katsushisa Ban. Under attack from the USS Chicago, the sub fired two torpedoes. One failed to go off; the other passed in front of the Chicago and under the Kuttabul, exploding against the wall of Garden Island naval base and demolishing the ferry.

Seaman Neil Roberts had just finished sentry duty on the Kuttabul and his relief watch offered him his bunk on the top deck. "That saved my life," Mr Roberts said. The casualties were all on the main deck, where he usually slept. In the pandemonium, the survivors swam to the island, thrashing through the debris and the bodies of their comrades.

Many were convinced an air raid had taken place. The last thing anyone expected was a submarine attack. Arriving at the scene, Admiral Gerard Muirhead-Gould barked at his underlings: "What are you lot doing, running up and down the harbour dropping depth charges and talking about enemy submarines?"

The following week, submarines shelled Sydney, reinforcing the realisation that - as one naval commander put it - "our isolation did not protect us from the horrors of war".

Mr Gonzalez said the film had been cathartic for the Japanese survivors, who had never talked about their experiences before. The war remains, to some extent, a taboo subject in Japan. Among those interviewed was Mr Ashibe's brother, Itsuo, still in deep grief 62 years on.

The sub containing his brother was never found. "I longed for a memento, a glove if nothing else," he said. "I kept thinking he might turn up at home one day."