China borders North Korea on the Yalu River.

中国与朝鲜以为界。

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

然后向中朝界进发。

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，防军会用绳索将货物从对岸拖过来，然后他再“孝敬”他们。

This presented MacArthur with the frustration of having planes from Chinese bases assault United Nations depots, supply lines, and troops and then retreat to their sanctuary north of the Yalu.

这让麦克阿瑟感到沮丧，因为中国基地的飞机袭击了联合国的仓库、补给线和部队，然后撤退到以北的避难所。