Fighter jets will roar over Beijing and tanks will rumble past Tiananmen Square on Wednesday when China’s top leader, Xi Jinping, presides over an elaborate military parade designed to stoke national pride and show off China’s diplomatic heft.

More than two dozen leaders, mostly authoritarian, are expected to attend. Joining Mr. Xi are President Vladimir V. Putin of Russia, the North Korean dictator Kim Jong Un and President Masoud Pezeshkian of Iran — the first time that the leaders of the four countries will gather in the same place.

China is using the parade to commemorate the 80th anniversary of the end of World War II. The event is designed to showcase some of the nation’s newest weapons and draw attention to what the ruling Communist Party asserts are China’s unrecognized contributions to the defeat of Imperial Japan.

Security has been tightened across Beijing in preparation for the parade. Rehearsals have involved more than 40,000 soldiers, civilians and staff. The parade route will proceed along Chang’an Avenue, a central thoroughfare that passes Tiananmen Square and the entrance to the Forbidden City.

Dictators, Neighbors, and One NATO State

Other guests who are expected to attend include Min Aung Hlaing, the chief of Myanmar’s junta and President Denis Sassou Nguesso of the Republic of Congo, leaders who hail from countries with abysmal human rights records. Only seven of the 25 countries whose leaders are attending are considered free or partly-free by Freedom House, a Washington-based advocacy group.

There is one notable outlier, Prime Minister Robert Fico of Slovakia, a NATO member state considered one of the freest countries in Central Europe. Mr. Fico, a longtime critic of Western support for Ukraine, has worked hard to forge better diplomatic and economic ties with Beijing.