It was hard to imagine a greater contrast. While China’s rulers were celebrating the 70th anniversary of the founding of the People’s Republic with an enormous parade of missiles and technological achievements meant to intimidate and impress, Hong Kong witnessed some of the most violent protests in four months of demonstrations against Beijing’s encroachment on the enclave’s autonomy.

There was no subtlety in either President Xi Jinping’s celebration of his country’s raw power, or Hong Kong’s rejection of the repressive rule behind that power. Something will have to give.

Mr. Xi was central to his show. Clad in a Mao suit, he made no mention of his immediate predecessors as he presided over an awesome display of what he calls the “ Chinese dream ,” a broad vision of China’s rise as an economic, military and police force to be reckoned with. “No force can shake the status of our great motherland, no force can obstruct the advance of the Chinese people and Chinese nation,” he declared.