Mr Biden was speaking in the Windsor pub in Dundalk on Wednesday night on the first day of his three-day visit.
The White House website attempted to smooth over the situation by clarifying its official record to refer to the All Blacks. However, Mr Biden’s error threw into question the president’s ‘partisan’ stance towards Northern Ireland and the Republic.
It also attracted fierce criticism online and from major media outlets. “Gaffe spoils Biden’s charm offensive,” said a Times headline. The New York Post called it a “cringeworthy gaffe”.
Here’s what you need to know about the Black and Tans.
What did Joe Biden say about the Black and Tans?
The US president, paying tribute to relative and former Ireland rugby player Rob Kearney, thanked him for the tie he was wearing. He referenced Ireland’s first victory over the All Blacks (a 40-29 win) at Soldier Field in Chicago in November 2016.
He said: “This was given to me by one of these guys, right here, was a hell of a rugby player. He beat the hell out of the Black and Tans.”
The delivery version of the speech on the White House website has the Black and Tans crossed out and “All Blacks” added in brackets.
Who were the Black and Tans?
The Black and Tans were a notorious group of British paramilitary forces that operated in Ireland during the early 20th century. A 10,000-strong group of British recruits to the Royal Irish Constabulary (RIC), they were sent to counter Irish Republican Army (IRA) extremism.
They were recruited from January 1920. Many of those who signed up were unemployed veterans, who had already served in the First World War.
They worked in Ireland to suppress the demands to break away from Britain.
During the War of Independence from 1919-21, many RIC members quit, as they were worried about reprisals and because of divided loyalties.
They were known for their brutal approach, but also faced extremists in the IRA whose tactics were also vicious.
The group was notably singled out in the pro-IRA song, Come Out, Ye Black And Tans, which is still popular with Irish rebel bands.
The Black and Tans were eventually disbanded in 1922 following the signing of the Anglo-Irish Treaty, which established the Irish Free State.
Why were they called the Black and Tans?
Their nickname originated from the colour of their uniform.
They wore some of the dark green clothing of the RIC, which looked black, and some of the khaki of the British army.