It was a 5-cent fare hike for Hong Kong's iconic Star Ferry that set off the protests. Cars and buildings were set on fire. Riot police patrolled the streets. Tear gas was fired — and still the crowds kept coming.

That was Hong Kong in the spring of 1966. And the violence didn't end there. A year later, leftists inspired by Mao Zedong's Communist Party launched a series of riots and bombings that killed 51 people in the British colony.

The Hong Kong Police Force — and the British military — employed emergency laws, sweeping raids and mass arrests, sometimes facing accusations of excessive force.