EIGHTEEN months ago, President Xi Jinping was in Hong Kong to preside at the inaugural ceremony of a new chief executive, John Lee, and his team. Mr. Lee had spent nearly his entire career in police and security work. The Chinese leader in his speech exhorted the new administration to move the Hong Kong Special Administrative Region — to use the city's proper title — to 'break new ground and achieve another leap forward' in the administration's five years.

That year, 2022, marked 25 years since Britain's handover of Hong Kong to China. Over most of that quarter century, Xi said, Hong Kong's economy had thrived, its status as an international financial, shipping and trading center had been maintained, and its innovative science and technology industries had been booming.