Hello. Unfortunately your question needs more information to be answered accurately. However, I will try to help you in the best possible way.
The people who lived around Huang He were attacked, because this region had soil with high fertility, which allowed those who dominated that region to have the possibility to produce agricultural products very efficiently, quickly and cheaply. in addition, the Huang He region was on a commercial route, which greatly improved the region's economy and trade. Not least, these people had easy access to water and fish, which could be removed from the river, the water could be used for irrigation, making agricultural production even more efficient.
Huang He is the second largest river in China and the region around it has been much coveted by invading peoples because of this reason.