Not many people are aware that there is a third Korea, in addition to what we call South Korea and North Korea.
Only oceans form effective borders, other-wise ethnic groups straddle borders. And, along the Yalu River, which forms much of the border between North korea and China, we find on the Chinese side of the River, a large Korean population in China's Dong-bei (the north-east). This area is shown in red,on the map below.
There are so many Koreans there, whose families have lived in China for generations, that the Chinese government has given them their own autonomous prefecture within the Jilin Province.Its called Yanbian.
The capital is called Yanji, pictured below. Both Korean and Chinese are official languages in Yanbian, but most ethnic Koreans are bi-lingual, increasingly so as China has become more prosperous.
You can see the sign on the building on the lower right of the image, has a sign in both Chinese characters and Korean alphabet.
and if you check the map, you'll see that in the North, Russia occupies a narrow strip of land that separates Yanbian from the sea. There's a popular lookout in Fangchuan National Scenic Area (below), from which you can see both Russia, and North Korea as you stand in China. This is part of the area that General Douglas MacArthur wanted to turn into a radioactive waste land by dropping nuclear bombs all along the border between China and North Korea.
