[Read live updates to China’s National Day parade and Hong Kong protests.]

President Xi Jinping on Tuesday presided over a large military parade and pageant involving 100,000 performers as China commemorated the 70th anniversary of Communist rule and its rapid emergence as a global power.

National Day is an important holiday in China’s political calendar and the authorities in Beijing have left little to chance: For weeks they have imposed an extensive security crackdown around the country and across the internet.

But as much as China wants to project a vision of itself as prosperous, powerful and unified, anti-government protests in Hong Kong threaten to overshadow the festivities.

Mr. Xi used his speech Tuesday to say that China would “maintain the lasting prosperity and stability” of Hong Kong, but he did not address the protests convulsing the city.