The Democratic senators Elizabeth Warren and Jeff Merkley have announced legislation that would strip Medals of Honor from US soldiers who carried out the Wounded Knee massacre, killing hundreds of mostly unarmed Native Americans.

A House bill on the subject was introduced in June by representatives including Deb Haaland, a New Mexico Democrat who is one of the first female Native American US lawmakers.

“The horrifying acts of violence against hundreds of Lakota men, women, and children at Wounded Knee should be condemned, not celebrated with Medals of Honor,” said Warren, from Massachusetts, who is campaigning for the Democratic presidential nomination.

“The Remove the Stain Act acknowledges a profoundly shameful event in US history, and that’s why I’m joining my House colleagues in this effort to advance justice and take a step toward righting wrongs against Native peoples.”

In a statement, Haaland said the act was “about more than just rescinding Medals of Honor from soldiers who served in the US 7th Cavalry and massacred unarmed Lakota women and children [in 1890] – it’s also about making people aware of this country’s history of genocide of American Indians.”

Donald Trump has referenced Wounded Knee in mocking Warren’s claim to Native American heritage.

The senators’ announcement came on Wednesday, a day before Thanksgiving, the federal holiday commemorating a 1621 harvest meal shared by Native Americans and Pilgrims. Thanksgiving has increasingly drawn criticism for glossing over the disastrous impact of white settlement on Native Americans.

Since 1970, the United American Indians of New England organisation has held a National Day of Mourning on Thanksgiving day, to remember “the genocide of millions of native people, the theft of native lands and the relentless assault on native culture”, according to the Associated Press.

The National Day of Mourning takes place in Plymouth, Massachusetts, an early place of European settlement.

Wounded Knee, described by the Washington Post as “one of most shameful and bloody acts of violence against indigenous people in American history”, occurred on 29 December 1890.

Chief Big Foot, who led the Minneconjou Lakota, was guiding his people to refuge in South Dakota when US soldiers stopped them. The group surrendered and was taken to Wounded Knee Creek, “surrounded by 470 soldiers and their formidable artillery”, the Post wrote.

While exact details of the massacre have proved difficult to determine, it is believed there was a dispute while soldiers were trying to disarm the chief’s men. It is also thought a gunshot prompted American forces to attack. Between 150 and 400 Native Americans were killed. Historians agree most of the victims were women and children.

Twenty members of the 7th cavalry involved in Wounded Knee received the Medal of Honor, which is described by the Army as “the nation’s highest medal for valor in combat that can be awarded to members of the armed forces”.

A large number of the medals were awarded for “gallantry” and “bravery” even though there are few details of purported acts of heroism, the Post noted.

Maj Gen Nelson A Miles, an army commander, wrote of the incident: “I have never heard of a more brutal, cold-blooded massacre than that at Wounded Knee.”

According to a letter cited by the Post, Miles described the victims as “women with little children on their backs, and small children powder-burned by the men who killed them being so near as to burn the flesh and clothing with the powder of their guns, and nursing babies with five bullet holes through them”.

While the Medal of Honor was granted more loosely in the 19th century, scholars have noted that the number of Wounded Knee recipients is high. Antietam, an 1862 civil war battle considered the “bloodiest day in US history”, also led to 20 awards.

Native Americans have long pushed for the revocation of medals awarded to Wounded Knee soldiers. Since 1997, the National Congress of American Indians has greenlighted resolutions requesting the removal of medals.

Congress formally apologized in 1990, stating “deep regret on behalf of the United States to the descendants of the victims and survivors and their respective tribal communities”. But, the Associated Press reported, lawmakers did not offer any type of reparations.

