Daofu, China ? Military convoys rumble along winding mountain roads, the Internet has been cut in potential trouble spots and motorists must run a gantlet of inspection checkpoints as Beijing mounts a show of force in Tibetan areas to prevent a repeat of uprisings against Chinese rule.

A volatile period begins Tuesday, the 50th anniversary of a failed revolt that sent the Tibetan leader, the Dalai Lama, into exile.

A year ago, Tibetans erupted in protest — sometimes violently. Today, checkpoints and garrisons seem as numerous as the fortress-like Buddhist monasteries and white-domed shrines that dot the steep slopes and pastures of western China bordering Tibet. The result is a kind of martial law, with constant tension across a third of Beijing’s territory.

In Daofu, a town in Sichuan province where Buddhist mantras are carved into the sides of 13,000-foot snow-dusted mountains, the streets where local nuns protested a year ago are calm. Officials say monasteries are closed to visitors, with monks remaining inside studying Buddhist scriptures.

While markets are bustling and many shopkeepers do brisk business, the atmosphere is steeped in watchfulness. Police cars and military trucks patrol dusty streets where prayer flags flutter from homes and Buddhist shrines.

Authorities have purged monasteries of suspected agitators and enforced denunciation campaigns of the Dalai Lama.

Rumors that the spiritual leader would be kidnapped by Chinese authorities touched off the uprising in Lhasa on March 10, 1959, nine years after the Communist army marched into the Tibetan regional capital.

Monks in Lhasa tried to stage a commemorative march last year, drawing a blockade by police. That set off protests that erupted into a riot against Chinese rule in Lhasa on March 14. Hundreds of shops were torched and ethnic Chinese attacked in the unrest that spread to dozens of communities before sputtering out last summer.