One of the last surviving second world war Darwin bombing veterans remembers the day war came to Australia’s backyard on the wings of 188 Japanese planes.

At the 75th anniversary memorial on Sunday, South Australian Mervyn Ey listened as air raid sirens rang out to mark the moment bombs were already raining destruction down on the city.

The alarm came too late three quarters of a century ago, when the then 20-year-old private and the rest of the undermanned Allied defence forces were taken by surprise.

“There wasn’t any warning … there were planes going everywhere and explosions everywhere,” Ey said.

“We were absolutely shocked by the force of it. We said ‘if this is war, God help us’.”

Japan’s deadly campaign brought a distant war to home soil, and the Northern Territory had become the front line.

It was the largest and most destructive single attack mounted by a foreign power on Australia and led to the worst death toll from any event in the nation’s history.

The assault was more savage than Pearl Harbor; more bombs fell on Darwin, more civilians were killed, and more ships were sunk.

Archival photo of Mervyn Ey, who is one of 29 veterans who returned to Darwin for the 75th anniversary of the bombing. Photograph: AAP

The governor general, Sir Peter Cosgrove, paid tribute to the 88 sailors killed on the USS Peary in Darwin Harbour – the American navy’s greatest loss of life in Australian waters.

“Although overwhelmed by Japanese dive bombers, the Peary went down all guns blazing, her crew full of spirit and defiance, fighting and firing to the very end,” Cosgrove said.

Ey can still picture smoke billowing from the ship wreckages, and men burning to death in the fiery, oily water. “One boat just blew to pieces,” he said.

Bombing of Darwin veteran Mervyn Ey, who remembers hearing the bombs whistling as they rained down on the city. Photograph: Lucy Hughes Jones/AAP

The 96-year-old said the government downplayed the scale of the devastation and it has remained a buried chapter in Australia’s history.

“The people hadn’t been told the whole truth about what happened … they didn’t want to scare the public,” he said.

He’s among 29 diggers who made the pilgrimage back to ground zero to make sure the horror of war won’t be forgotten.

The prime minister, Malcolm Turnbull, and the opposition leader, Bill Shorten, joined dignitaries from Japan and the US at the commemorative service.

There was a military depiction of the day’s events in 1942, before a four-aircraft flyover and a minute’s silence to remember those who lost their lives.

Before laying a wreath at the ceremony, Turnbull praised the enduring bond between Australia and the US that was forged through battles like the bombing of Darwin.

“Here in Darwin and around the world our two nations continue to serve shoulder to shoulder, partners,” he said. “Your sacrifice and the sacrifices of the people of Darwin will never be forgotten.”

Darwin resident Wendy James was evacuated to Perth when she was six. Now 81, she remembers air raid sirens ringing and her parents arguing in their home when she heard a loud banging on the front door.

Wendy James remembers evacuating Darwin at age six. Photograph: Lucy Hughes Jones/AAP

“A huge military policeman walked in and said ‘you have to leave immediately’,” James said.

She was one of the 2,000 women and children evacuated from Darwin to all parts of the country, and she remembers waving goodbye to her father from the wharf. “We didn’t realise that we weren’t going to see him for three years,” she said.

Her family moved from house to house while they waited out the attacks up north with little information about the fighting.

All of James’ father’s letters fell out of the envelope in pieces. “Anything that mentioned the bombing … had been cut out [by censors]. So we ended up with all these strips of paper,” she said.

“But at least we’d heard from him. His signature was at the bottom, so we knew he was alive.”

When James returned to Darwin in 1945, her town was unrecognisable –devastated by 18 months of air raids.

School wouldn’t resume for a year, so the then 10-year-old roamed old army camps, playing with ammunition that had been left behind.

“My brother and I went around on bicycles trying to find the Darwin we remembered,” she said.

“We went looking for the house we’d lived in, and it had disappeared. Chinatown had been completely wiped out.”