The truth of Australia’s history has long been hiding in plain sight.

The stories of “the killing times” are the ones we have heard in secret, or told in hushed tones. They are not the stories that appear in our history books yet they refuse to go away.

The colonial journalist and barrister Richard Windeyer called it “the whispering in the bottom of our hearts”. The anthropologist William Stanner described a national “cult of forgetfulness”. A 1927 royal commission lamented our “conspiracy of silence”.

But calls are growing for a national truth-telling process. Such wishes are expressed in the Uluru statement from the heart. Reconciliation Australia’s 2019 barometer of attitudes to Indigenous peoples found that 80% of people consider truth telling important. Almost 70% of Australians accept that Aboriginal people were subject to mass killings, incarceration and forced removal from land, and their movement was restricted.

The Killing Times is a Guardian Australia special report that aims to assemble information necessary to begin truth telling – not just the grim tally of more than a century of frontier bloodshed, but its human cost – as told by descendants on all sides. This is the history we have all inherited.

Our interactive map details massacres in every state and territory but the research is ongoing. It does not count all the sites of conflict, or clashes over land and resources, in which lives were lost in the colonisation of Australia.

The numbers we have drawn on are conservative estimates.

There are more massacre sites to be added – places where the true death toll may never be known – and many more we are still working to verify, particularly in Queensland, Western Australia, the Northern Territory and New South Wales.

In this first snapshot of the continent, we have found that there were at least 270 frontier massacres over 140 years, as part of a state-sanctioned and organised attempt to eradicate Aboriginal people.

An 1888 drawing of a massacre by Queensland’s native police at Skull Hole, Mistake Creek, near Winton. A Norwegian scientist, Carl Lumholtz, drew it after being shown ‘a large number of skulls of natives who had been shot by the black police’ several years earlier. Illustration: State Library of Queensland

Starting in 1794, mass killings were first carried out by British soldiers, then by police and settlers – often acting together – and later by native police, working under the command of white officers, in militia-style forces supported by colonial governments.

These tactics were employed, without formal repercussions, as late as 1926.

Using data from the colonial massacre map at the University of Newcastle’s Centre for 21st Century Humanities, and adopting its stringent research methods, Guardian Australia has surveyed the rest of the country.

We found that:

Government forces were actively engaged in frontier massacres until at least the late 1920s.

These attacks became more lethal for Aboriginal people over time, not less. The average number of deaths of Aboriginal people in each conflict increased, but from the early 1900s casualties among the settlers ended entirely – with the exception of one death in 1928.

The most common motive for a massacre was reprisal for the killing of settler civilians but at least 51 massacres were in reprisal for the killing or theft of livestock or property.

Of the attacks on the map, only once were colonial perpetrators found guilty and punished – in the aftermath of the Myall Creek killings in 1838.

In NSW and Tasmania between 1794 and 1833, most of the 56 recorded attacks were carried out on foot by detachments of soldiers from British regiments, and an average of 15 people were killed in each one. The weapon most often used was the “Brown Bess” musket, which was issued to British forces in the Napoleonic wars.

In NSW and Victoria between 1834 and 1859, horses and carbine rifles were used in at least 116 frontier massacres of Aboriginal people in mostly daytime attacks, with an average of 27 people killed in each attack.

From the late 1840s, massacres were carried out as daylight attacks by native police, sometimes in joint operations with settlers. They most often used double-barrelled shotguns, rifles and carbines.

Preliminary data from Queensland shows that between 1859 and 1915 an average of 34 people were killed in each attack.

There are at least nine known cases of deliberate poisoning of flour given to Aboriginal people.

There were also efforts to cover up the atrocities.

In 1927 a royal commission into the Forrest River massacre in Western Australia concluded that a police party had killed at least 11 people then burned their bodies in makeshift ovens. In his report the commissioner, GT Wood, said a “conspiracy of silence” in the entire Kimberley district had thwarted attempts to find out what really happened.

Many kartiya [whitefellas] were too greedy for our land and didn’t see us as fully human Francis Jupurrurla Kelly

These massacres are challenging to read about. It can be even more challenging to discover a personal or family connection to them. Nevertheless, many Australians have come forward to share their stories, some for the first time.

Sandy Hamilton is descended from a soldier in the 46th Regiment which, on orders of the NSW governor Lachlan Macquarie, killed at least 14 Aboriginal people at Appin in 1816.

“We need to take ownership of our history,” Hamilton says. “We deserve to know the truth of how we came to be who we are.

“Then we can also make real choices about who we want to be as a society, as Australians.”

Liza Dale-Hallett is a great-niece of George Murray, a police constable who led the killings at Coniston in 1920, in which at least 50 Aboriginal men, women and children died. Warlpiri, Anmatyerre and Kaytetye people say up to 170 were slaughtered.

“It happened all over Australia and this is a part of our history,” Dale-Hallett says. “I’ve got a direct connection to it – but that doesn’t make it my history and not yours.

“Part of the reason they are continuing to cause harm is they haven’t been properly acknowledged. The simple act of listening is a really important first step in a more complex conversation that needs to be had about how did Australia settle itself.”

Willowra women embrace at the 90th anniversary of the Coniston massacre in 2018. Photograph: Central Land Council

A descendant of Coniston survivors, Francis Jupurrurla Kelly, agrees.

“We want everyone to understand why so many of our innocent men, women and children were murdered in cold blood,” he says.

“Many kartiya [whitefellas] were too greedy for our land and didn’t see us as fully human.

“We can only come together as one mob, if everyone, starting with all our schoolchildren and our elected representatives, knows what has happened to our loved ones and why, so they are never forgotten.”

In replicating the University of Newcastle’s centre’s data collection methods we have only recorded attacks in which six or more people were killed.

According to the centre’s Prof Lyndall Ryan, the massacre of six undefended Aboriginal people from a hearth group of 20 is known as a “fractal massacre”, so called because it leaves survivors vulnerable to further attack and far less able to hunt, care for children or carry out cultural obligations to country.

Research and verification of the evidence takes time and care. It involves locating primary sources such as letters, journals, newspaper articles, books, photographs and oral histories.

Standing stones commemorate the Flying Foam massacres of 1868 which began at this site overlooking King Bay in Western Australia.

Photograph: David Dare Parker/The Guardian

We have relied on the written record of the time but acknowledge that, for example, a settler’s journal is not necessarily a reliable or definitive account of what took place. There can be a tendency to understate the severity of the attacks, the toll they took and the actions of those present.

The written records don’t always indicate intention. Sometimes they do, in chilling detail, as described in this letter from a Gippsland squatter, Henry Meyrick, to his family in England in 1846:

The blacks are very quiet here now, poor wretches. No wild beast of the forest was ever hunted down with such unsparing perseverance as they are. Men, women and children are shot whenever they can be met with … I have protested against it at every station I have been in Gippsland, in the strongest language, but these things are kept very secret as the penalty would certainly be hanging.

We have categorised killings according to the alleged reasons for them as written in primary sources we have seen, but oral histories provide context. Aboriginal attacks on settlers often took place after previous unreported killings of smaller groups or individuals, or as the result of escalating tensions over land, water and resources. Settler reprisals were heavily disproportionate and grew worse over time.

Liza Dale-Hallett, a historian and great-niece of the man who led the Coniston massacre, at the border of the Northern Territory and Queensland. ‘The simple act of listening is a really important first step,’ she says

The language in these sources is coded. “Dispersal” is a common euphemism. “Land clearing”, “expeditions” and “hunting parties” were undertaken to “teach the blacks a lesson”.

Learning about this history will come as a shock to some. But Australians trying to move past blame or guilt are coming forward now in greater numbers, and their voices are only growing louder.

“We have done a lot already to make sure nobody has an excuse to stay ignorant,” Francis Jupurrurla Kelly says. “It’s now time for governments and others to do their bit to tell the truth and help us move forward together.”

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