The U.S. military is so powerful, so why doesn’t it dare station troops in any of China’s 14 land-bordering neighbors?

China has an unofficial 500-kilometer defensive perimeter. It has never been explicitly declared, but the major powers all know about it.

We openly entered both the Korean War and the Vietnam War because China was unwilling to let powers from outside the region approach its densely populated areas.

Here is something many people may not know:

Around 2013, the U.S. military conducted joint exercises with Thailand, allegedly intending to turn them into a military intervention in Myanmar. China was alarmed and deployed 200,000 troops to Yunnan, replacing the border units of the People’s Armed Police and conducting military exercises of its own.

Both sides later withdrew their forces.

China is extremely sensitive to extraregional powers approaching its borders. This is also one of the reasons why it has not established formal diplomatic relations with the Taliban.