In the 1930s, when students, supported by underground operatives of the C.C.P. (which was illegal then), took to the streets to demand that Chiang Kai-shek’s ruling Nationalist Party do more to protect China from Japan, they invoked the “May Fourth spirit.” The Nationalist Party also claimed that it best exemplified that spirit. The contest to appropriate the legacy of Wusi was on.

Come 1989, it was the leaders of the C.C.P. themselves — by then long in power — who were targeted by a fresh generation of students calling for a “New May Fourth Movement.”

Once again, the most important site of protests was Tiananmen. In the 1950s, the area in front of the gate had been turned into a square filled with monuments, including one at the center honoring China’s revolutionary heroes. A frieze at the foot of that central structure depicts young men and women taking to the streets in 1919. It was in front of it that the students of 1989 set up their main base of operations.

On May 4 of that year, as the C.C.P. commemorated the 70th anniversary of Wusi inside The Great Hall of the People, to one side of Tiananmen Square, the protesters held a competing event on the plaza. Once again, two opposing political camps were both claiming the mantle of the 1919 movement. Exactly one month later, the People’s Liberation Army rolled in, killing hundreds, probably several thousands, of demonstrators and residents.

What are widely known in the West as the “Tiananmen Square” protests are called “Liusi Yundong,” or the “June Fourth Movement,” in Chinese — a reference to the day of the massacre in 1989, of course, but also an echo of the uprising of 1919.

And yet today, while “Wusi” appears in many online and print publications across the Chinese mainland, “Liusi” is taboo.

Under President Xi Jinping, the C.C.P.’s efforts to control the meaning of the Wusi protests have continued unabated. The movement holds a revered place in official chronologies, as a turning point and the start of modern times in China. The party, playing on the kind of national pride extolled back in 1919, boasts today that China no longer appeases, but leads, on the international scene.