Crowds took their seats at Beijing's Tiananmen Square on Tuesday for a huge military parade to celebrate 70 years of Communist Party rule.
A phalanx of tanks and other military hardware will roll across Tiananmen Square under the gaze of President Xi Jinping, the country's most powerful leader since Mao Zedong, who founded the People's Republic of China on October 1, 1949.
New weapons - including a hypersonic drone and an intercontinental ballistic missile whose range encompasses the United States - are expected to make their public debut, according to Paris-based analysts.
"Unity is iron and steel. Unity is a source of strength," Xi said in a speech on Monday evening.
But behind the festivities, a clutch of challenges tests Xi's ability to maintain economic and political stability.
The major challenge is Hong Kong, where pro-democracy protesters hit the streets early in a bid to grab the spotlight from Beijing, with a series of rallies against what they see as the erosion of their special freedoms.
Hong Kong police said they were expecting violence across the city, warning it could be "very, very dangerous", while masked protesters said that "in the face of tyranny, we can only fight as if our last battle".
Officers fanned out across the territory and small pockets of demonstrators marched through the streets, while local officials watched a flag-raising ceremony behind closed doors.