The outbreak of World War I changed the lives of more than 100,000 Germans living in Australia.

Many were labelled "enemy aliens" and jailed without trial or the ability to appeal against their detention.

Most inmates were ultimately deported in 1919 in a Government-backed form of ethnic cleansing.

This changed the fabric of the nation because during the 19th century, Germans were the largest non-English-speaking group in Australia.

From the 1850s, migrants were targeted for their skills in wine-making and agriculture, and played a critical role in building these industries in South Australia and Queensland in particular.

But in 1914, men who were old enough to join the army were detained in makeshift camps across the country.

The next year, they were shipped to three main centres in New South Wales: Berrima in the Southern Highlands, Trial Bay on the state's North Coast and the largest camp at Holsworthy, south-west of Sydney.

Nadine Helmi wrote about their experiences in her book, The Enemy at Home: German Internees in WWI Australia.

"It was really terrible for people who had lived here for years and years - 30, 40 years or even born here," she wrote.

People who'd been respectable citizens and loyal to Australia were treated "like criminals and interned. The civil rights for those people had been taken away".

A teacher and German children at the internment camp at Berrima in New South Wales in 1917. ( Australian War Memorial )

Doing business with the 'German Huns'

Anti-German sentiment was fierce. Recruitment posters at the time depicted an Australia over-run by Germany.

Sorry, this video has expired Rudolph Schneider's grandsons speak with the ABC

Schools were closed. Music was banned. Whole communities were renamed, erasing their German heritage.

Brothers Benno and Leo Glockemann visited Holsworthy to retrace the steps of their grandfather, Rudolph Schneider.

Born in Germany, Schneider moved to Australia when he was 18 and was later naturalised.

And as Benno Glockemann would discover, a newspaper article asked why the government was allowing Schneider to do business with the "German Huns".

"He was never disloyal. Trading with the enemy - trading with German colonies; well, that was a business," he said.

Schneider was detained for four years.

His family left their Mosman mansion, moving to the country where anti-German hysteria was so prevalent the children didn't attend school.

A propaganda poster depicts a German ogre, his blood-covered hands and forearms clutching at a globe of the world. Blood pours over Europe and slowly oozes towards other countries, demonstrating the threat of the German menace and the need to contain it. ( Australian War Memorial )

Leo Glockemann says the impact is still being felt today.

"Wars have such a profound effect on everybody," he said.

"It's not just the fallen. It's not just the soldiers - it's everybody. And it takes generations for a war to work its way out of the system."

Schneider was one of the fortunate few who would stay in Australia.

Of the 7,000 detainees, only 300 remained. The rest were deported.

Nadine Helmi said it was a devastating blow that fractured families.

Some fathers never saw their children again, "So they went back to a Germany where they didn't have any links".

"Some couldn't even speak German when they were deported. The ships took them away to a Germany that I have to say was also of course completely wrecked and ruined by the war," she said.

German origin hidden from children by their parents

And in an extraordinary twist, the Glockemann brothers themselves were detained as children during World War II.

Anti-German policies affected three generations of this family, many years after they first called Australia home.

"That was the end of the German community as a visible community," Helmi said.

"Of course Germans still lived here, and when I say Germans I mean German-Australians.

A recruitment poster playing on anti-German sentiments. ( National Library of Australia )

"But they kept a very low profile."

Helmi said being of German descent was a secret often hidden from children by their parents.

"Germans changed their names and didn't talk German ... so they kind of disappeared off the radar," she said.

Today there are echoes of the lives lived by detainees at the Holsworthy Army Barracks.

The internment camp is long gone but the ruins of the officers' mess remains - as does the on-site jail.

Graffiti in the solitary confinement cells dates back to World War I.

Detainees carved their names into the stone walls. One reads "Germania" and is dated 1917.

"It's a rich tapestry of who's been in these buildings over the past 100 years," Liverpool Military Area regional environment officer Robert Kolano said.

The walls bear the names of men detained during both World Wars - a poignant reminder that this started with a conflict that was supposed to end all wars.