On a chilly 11 December in 1917, 13 black soldiers were sent to their deaths. None of the men made any attempt to resist as they were taken from the trucks to the scaffold, where ropes dangled forebodingly from the crossbeam. A few shivered, but that was attributed more to the cold than fear. “Not a word out of any of you men now!” Sgt William Nesbit proclaimed to the other 12 before the final moment.

Fast forward 100 years to the recovery efforts after Hurricane Harvey devastated Houston. During the clean-up, workers found vandals had sprayed red paint over a historical marker at the former location of Camp Logan, a military encampment in the early 1900s. The marker had recently been rededicated to commemorate the 100th anniversary of the 1917 Houston riot which had led to the soldiers’ untimely deaths.

The seemingly racially charged act of vandalism served to obscure the part of the inscription explaining how the Third Battalion of the 24th United States Infantry — a predominantly black unit assigned to guard the camp during its construction in the first world war — had mounted an armed revolt as a result of the racist treatment they received while stationed in Houston.

“They sent these soldiers into the most hostile environment imaginable,” says Charles Anderson, a relative of Sgt Nesbit. “There was Jim Crow laws, racist cops, racist civilians, segregated streetcars, and the workers building the camp hated their presence too.”

The soldiers’ experiences over seven fractious weeks in Houston serve to illustrate the impact structural racism had on the home front during wartime. A hundred years on and this racism remains deeply entrenched in American society, as evidenced by the vandalised marker and, more broadly, the violence inflicted on non-white communities by the state — particularly the police.

“The soldiers were standing up for America when it wasn’t standing up for them,” says Paul Matthews, founder of Houston’s Buffalo Soldiers National Museum, which examines the role of black soldiers in US military history, including an exhibit about the executed soldiers. “The riot was a problem created by community policing in a hostile environment.”

Although the majority of the soldiers were raised in the south and were familiar with segregation, as army servicemen they expected fair treatment during their service in Houston. But local police and public officials viewed the presence of the black soldiers as a threat to the established racial hierarchy. The sight of black men wearing uniforms and carrying guns incensed white residents, who worried that by showing black soldiers the same respect as their white counterparts, black residents might come to expect similar treatment.

The soldiers themselves were angered by the ‘whites only’ signs, the racial slurs they received from white Houstonians and streetcar conductors who demanded they sit in the rear. In this charged environment, tensions mounted and minor conflicts ensued. That is, until 23 August, when two Houston police officers pistol-whipped and arrested a member of the battalion, Pte Alonzo Edwards, for interfering with their violent arrest of Sara Travers, a local black woman. When one of the battalion’s military policemen, Cpl Charles Baltimore, went to inquire about Edwards’ arrest, an argument with the officers ensued, resulting in one of them shooting at Baltimore and then arresting him.

Meanwhile, rumours – which turned out to be false – reached Camp Logan that Baltimore had been shot and killed and that a white mob was approaching the camp. After weeks of discrimination while living in Houston, strained nerves snapped; more than 100 soldiers grabbed rifles and headed into downtown Houston. During the two-hour riot that followed, 16 whites were killed, including five policemen.

The next day, martial law was declared in Houston and the unit was dispatched back to its base in New Mexico. Three courts-martial shortly followed – the first trial of 64 men proved the largest in US military history – during which a total of 118 enlisted black soldiers were indicted. 110 were found guilty, 19 hanged and 63 given life sentences.

“It was a dark rainy night during the riot,” Anderson says. “At the trial, the civilian witnesses used the n-word and couldn’t identify a single soldier firing shots that killed people.” Seven mutineers agreed to testify against the others in exchange for clemency. All the accused men pleaded not guilty. “The men did not have a fair trial,” says Sandra Hajtman, great-granddaughter of one of the policemen who was killed. “I have no doubt that those who were executed had nothing to do with the deaths.”

In Houston, a rapidly growing city, knowledge of the event is mixed. Most newcomers know nothing about this uncomfortable part of the city’s history that has for so long gone undiscussed. “It’s not the sort of thing that builds tourism,” says Mike Vance from the Heritage Society of Houston. “The city leaders might not trumpet it, but it remains part of the collective memory of the populace – I think that’s true of things as recent as the race riots of the 1960s in places like Detroit and Philadelphia and even the Rodney King riots in LA.”

But according to Lila Rakoczy, programme coordinator of military sites and oral history programs at the Texas Historical Commission, the centennial of the American entry into the first world war has brought a heightened awareness of such events and emboldened people to address the sensitive subject. “What happened at Camp Logan is a complex narrative to navigate,” Rakoczy says. “Americans take great pride in military service, but obviously pride isn’t at the forefront of people’s minds over what happened here. There was no public acknowledgment of it for a long time, but now there is more willingness to address it.”

Relatives of the executed soldiers remember growing up hearing their families discuss the soldiers, which often served as the catalyst to learn more. “At first, my family were upset when I started looking into it,” says Jason Holt, a relative of Pte Hawkins, one of the hanged soldiers. “To them it was very personal.” Holt has a century-old letter written by Hawkins to his mother the night before his execution, telling her of his innocence and not to be upset about him taking his “seat in heaven”.

Earlier this year, Angela Holder, great niece of Cpl Jesse Moore and a history professor at Houston Community College, helped lobby for gravestones from the Veterans Association for two soldiers killed during the riot. But more still remains to be done.

“We tried during the Obama presidency for a posthumous pardon and were on the list but missed out,” says Holder. “Perhaps we can approach a Texas politician or the National Association for the Advancement of Colored People to help.”

Earlier this year, petitions for the pardons were sent to the White House. The relatives are still awaiting a response as the 100th anniversary of the day of the execution comes and goes. But they aren’t giving up on remembering and telling others.

Holder drove me in her Mini Cooper around the Houston streets that her great uncle and his fellow soldiers marched down a century ago. Almost all are gentrified now; full of expensive-looking houses down which residents, of which an overwhelming majority are white, walk their dogs and relax under the Texas sun.

A peaceful, well-tended park surrounds the now cleaned-up historical marker. Part of the Texas Historical Commission’s marker programme, it differs from a monument in that it is an educational tool. That said, the small print of its message is easy to miss. “This is America, this is its history,” Matthews says. “Someone took power and did someone wrong – that’s who we are.”

Now though, it’s time to start making things right.