BEIJING — As Presid ent Xi Jinping watched from a rostrum above the iconic portrait of Mao, the weapons came one after the other down the Avenue of Eternal Peace, a propaganda-filled show of force to celebrate the 70th anniversary of Commun ist rule in China. Intercontinental ballistic missiles capable of delivering multiple nuclear warheads. Drones built for precision strikes. Tanks and armored personnel carriers bearing soldiers in green uniforms.

In an era when China plays a dominant role on the global stage, foreign officials, whether in Washington or Moscow or Hanoi, use such events to discern the intentions of Mr. Xi and determine whether the economic juggernaut of China is a political and milit ary threat. And the festivities on Tuesday sent a clear message at a complicated time for China’s diplomacy.

With the parade and policies like the militarization of the South China Sea, Mr. Xi and other Communist Party leaders want to tell the world: We are ready to fight and to seize or protect what we deem is ours. They want to show that China is not the same nation they say was humiliated by European powers and Japan from the 19th to 20th centuries.