IN PERHAPS the most important speech of his career, Chinese leader Xi Jinping on Wednesday promised "a new era" that "sees China moving closer to center stage" as "a leading global power" with a "world-class" military. Given how else he described the regime he intends to fashion over the next few years, that prediction ought to concern the world's democratic nations.

A decade and more ago, the United States and other Western leaders were urging China to become a global "stakeholder." But the superpower that Mr. Xi intends to lead doesn't look like the cooperative partner and gradually liberalizing society they imagined. Instead, China's 64-year-old ruler, having concentrated power in his own hands, now seeks to reinforce the authority of the Communist Party in all areas of life, at the expense of the rule of law, political dissent, private enterprise and even privacy itself: A new system of social monitoring will minutely record and rate the activities of every citizen, while storing their facial images for easy recognition.

While offering token mentions of markets, private enterprise and openness to foreign investment, Mr. Xi promised to help state companies become "stronger" and "bigger." He touted his "belt and road" initiative, a centrally directed project to pour hundreds of billions of dollars of infrastructure investments into countries across Eurasia.

Most of all, his vision of China as a superpower was infused by a nationalist agenda. In an address that stretched for three hours and 25 minutes, Mr. Xi intoned the phrase "strong power" or "great power" 26 times, according to a New York Times count. Mr. Xi boasted that one of his regime's most internationally controversial actions, the fortification of islets in the South China Sea, was a highlight of his first five years in office, even though an international tribunal found Beijing to be acting contrary to international law.

Mr. Xi's biggest applause line was a vow to "never allow anyone . . . at any time or in any form, to separate any part of Chinese territory from China." That would include Hong Kong and Taiwan, along with those disputed rocks. But he said nothing about North Korea or its manic pursuit of a nuclear arsenal, the crisis that most demands China's responsible cooperation.

The remaining few days of the party congress Mr. Xi kicked off will reveal how much his personal power will be bolstered. Analysts suspect his neo-totalitarian ideology will be written into the party's constitution, putting him on a par with Mao Zedong and Deng Xiaoping. They will watch to see whether a successor is positioned to replace him after a second five-year term, or whether Mr. Xi will entrench himself in the style of Russian President Vladi­mir Putin.

The question of whether Mr. Xi's strategy of party and state dominance can succeed in making China the world's leading power will take far longer to play out. There's reason to doubt that the command-and-control policies that failed in the 20th century can be made to work in the digital age. But China's ambitious ruler does have one big advantage. Thanks to the disarray of the U.S. political system and the retreat by two successive presidents from America's global role, an ambitious regime may find a vacuum to fill.