As the US continues its withdrawal from the Afghan capital, social media has been flooded with pictures of a helicopter evacuating people from the American embassy in Kabul.

It's a familiar image to some.

Back in 1975, photographer Hulbert van Es snapped a now-iconic picture of people scrambling into a helicopter on a rooftop in Saigon, at the close of the Vietnam War.

Analysts and US lawmakers - both Republican and Democrat - have been comparing the so-called fall of Saigon with the Taliban takeover of Kabul.

What was the fall of Saigon?

The Vietnam War was a conflict between the communist government of North Vietnam, and South Vietnam and its principal ally, the US.

It was lengthy - lasting almost 20 years - costly for the US, and extremely divisive among Americans.

The phrase "the fall of Saigon" refers to the capture of Saigon, the South Vietnamese capital, by communist forces of the People's Army of Vietnam, also called the Viet Cong.

Saigon was taken by the Viet Cong on 30 April 1975.

Against the backdrop of the Cold War, the North was supported by the Soviet Union and other communist allies, while the South was backed by Western forces - including hundreds of thousands of US troops.

America withdrew its military from South Vietnam in 1973, and two years later the country announced its surrender after the Northern forces took Saigon - later renaming it Ho Chi Minh City, after the late North Vietnamese leader.

Like Kabul, the city's capture came much quicker than the US had expected.

In response, the US abandoned its embassy in Saigon and evacuated over 7,000 American citizens, South Vietnamese and other foreign nationals by helicopter - a scramble known as Operation Frequent Wind.