MAQU, China — Enraged nomads stormed through this windswept town on the Tibetan plateau a year ago this month, raiding a police compound, setting fire to squad cars and forcing police officers to flee. To the north, Tibetans on horseback galloped into a schoolyard, ripped down a Chinese flag and hoisted a Tibetan one, shouting “Free Tibet!”

Now, the authorities have imposed an unofficial state of martial law on the vast highlands where ethnic Tibetans live, with thousands of troops occupying areas they fear could erupt in renewed rioting on a momentous anniversary next week. And Beijing is determined to keep foreigners from seeing the mass deployment.

In monasteries and nomad tents, villages and grasslands, the fury of Tibetans against Chinese rule has raged continuously since last year’s riots and the violent repression that followed. They are aware, too, that March 10 marks the 50th anniversary of a failed revolt against Chinese rule that led to the Dalai Lama’s flight into exile in India.

Signs of simmering resistance abound: Just last week, many of China’s six million Tibetans chose not to celebrate Losar, the Tibetan New Year, in order to mourn Tibetans who suffered during last year’s clashes. Monks have held rallies in parts of Qinghai and Sichuan Provinces. Last Friday, a monk from Kirti Monastery in Sichuan lighted himself on fire in a market, prompting security officers to shoot at him, according to Tibetan advocacy groups. Local officials deny the shooting.