"We all know this valley is important. I even want to spot terrorists here so that we can catch them. If one comes, we will catch one," he said.

"If 100 come, we will catch 100."

Beside outposts, the troops in the Wakhan Corridor have to routinely patrol China's borders with the three countries.

Half of the appointed patrol areas of Mingtiegai company are in mountainous areas above 4,000 meters with no roads. The soldiers have to ride horses and yaks in the winter, Tang said.

All companies have stables and the horses come from a military base. Most of them are Ili horses－a Xinjiang breed adapted to the high-altitude environment that can endure long distances.

Sometimes, it may take more than a week for the troops and their "war horses" to reach and return from the checkpoints at altitudes of 5,000 meters. Even during the summer months on the Pamir Plateau, climbing over snow-covered mountains and glaciers are something the soldiers have to deal with.

"The horses are fellow soldiers and they are very smart. They are miserable when we ride them to assigned checkpoints because they know it is very tiring. When we head back, you can tell that they are so happy to go home and they know the way," Tang said while grooming his horse "big red".

Liu Jianmin, 30, commander of the Kalaqigu company in the corridor, was busy preparing the horses for a routine patrol starting the next day.

"We patrol more frequently now. Even the horses have lost weight."

Kalaqigu means "black hole" in the Kyrgyz language because the area always experiences strong winds. It is on the east side of the Wakhan Corridor and just off the road to Khunjerab, the land port between China and Pakistan.

Huang Xiaoming, commander of the PLA's Khunjerab company, was busy analyzing images taken by the high-definition surveillance cameras on the mountain passes leading to Pakistan. He zoomed in to check a man on a horse heading to one of the passes.

"It's just a local herdsman. Nothing to worry about, " he said.

Power supply

After power lines were connected to the company's headquarters and frontier defense stations in July, the troops could monitor the border areas 24 hours a day without being worried about unstable power supplies from the solar panels.

Previously, the company's base was powered by solar panels and a diesel engine. When it snowed, little electricity was generated. Electricity is essential, if surveillance cameras are to monitor suspicious activities, and it will improve the troops' ability to catch terrorists or separatists trying to cross the border illegally.

Huang said some tribal terrorist cells in Afghanistan remain active near the Wakhan Corridor, posing a big threat to China, which has experienced a series of terrorist attacks.

Some separatists and terrorists who plotted attacks in Xinjiang were also trained in Pakistan and Afghanistan.

According to the State Grid, the electricity supply will be connected to the corridor later this year.

"The patrols are still the most effective way to detect abnormal border activities because we can track footsteps and find burnt wood, which terrorists could have used to make fires," Huang said.

One of the frontier defense stations of Huang's company is near the Khunjerab boundary marker, at an altitude of 5,200 meters. An inspection station of the border defense forces that belongs to the Ministry of Public Security mainly carries out inspections on people and goods passing the Khunjerab land port.