The Florida Klansmen had armed themselves with ax handles.

It was Aug. 27, 1960 — a year of lunch counter sit-ins by civil rights activists. The opening salvo had been fired on Feb. 1, when four Black college students sat down at a Whites-only lunch counter inside an F.W. Woolworth five-and-dime store in Greensboro, N.C. By spring, sit-in campaigns led by young African Americans had been organized in cities all over the South — including Lexington, Ky., Little Rock, Baltimore, Richmond and Nashville.

Surprised White onlookers spat and spewed racial epithets at the demonstrators and sometimes physically attacked them. But as spring blossomed into summer, white supremacists farther South, having watched the protests achieve success elsewhere, switched to high alert.

[Images of lunch counter sit-ins fueled the civil rights movement]

So when young Black people began staging sit-ins at a Whites-only Woolworth lunch counter in downtown Jacksonville, Fla., that summer, the Ku Klux Klan organized.

On the morning of what has become notoriously known as “Ax Handle Saturday,” more than 200 White men wielding wooden ax handles launched a vicious attack on Black protesters and passersby.

Before pulling the plug on an in-person convention in Jacksonville, President Trump was scheduled to speak there on the 60th anniversary of Ax Handle Saturday, angering local activists. Now he will accept the nomination in a speech from the White House, which is surrounded by fencing after repeated Black Lives Matter protests.

In 1960, the Klan attack in Florida signaled a sharp turn in the cascading sit-in movement, from spontaneous acts of racism to coordinated white supremacist brutality, according to Stanford University history professor Clayborne Carson.

“As [the protesters] began to achieve some success in the upper South, then in the Deep South areas, resistance became more intense,” said Carson, who is also founding director of the Martin Luther King Jr. Research and Education Institute at Stanford.