China borders North Korea on the Yalu River.

中国与朝鲜以鸭绿江为界。

Then they moved toward the Yalu River, the border between North Korea and China.

然后向中朝边界鸭绿江进发。

The soldiers at the border would pull the merchandise across the Yalu river with ropes, he says, and he would pay them off.

他说，边防军会用绳索将货物从绿鸭江对岸拖过来，然后他再“孝敬”他们。