Echoing methods which have already been used to control Uyghurs in Xinjiang, the Chinese government has tightened its grip around Tibet by securing an already nearly impassable border with drones, facial recognition and radar.

In the race to build a truly effective wall, China provides a model with a unique goal: keeping oppressed minority Tibetans within the country. For decades, the region’s daunting topography made this task difficult. The frontier between Tibet, which was occupied and annexed by China in the 1950s, and South Asia is a vast space, extending for more than 4,500 kilometers. The border falls mostly along the Himalayas, and the distance and remoteness of this region made a physical wall impractical.

The border’s near impenetrable nature was also a lifeline: from 1959 until 2008, thousands of Tibetans a year made the arduous trek across the mountain range to safety. Today, there are an estimated 150,000 Tibetans living abroad, in India, Nepal, or western countries including the U.S. and Canada. Nearly all can trace their freedom to a perilous Himalayan journey that was difficult for Chinese occupying forces to patrol effectively.

Until now. In recent years, the flow of refugees from Tibet has almost completely stopped. In 2007, about 3,000 Tibetans entered India; that number dwindled to only 80 by 2017. The reason is not, as China wants the world to believe, an improving situation in Tibet – in fact, nearly every human rights group believes repression there is at its highest level in decades.