Why did the Central Plains people help nomadic people resist Song Jun during the Northern Expedition in the Southern Song Dynasty?

Because the Central Plains people in the Southern Song Dynasty had no sense of national identity.

Both modern people and the authorities in the Southern Song Dynasty take it for granted that as long as the imperial court can declare the Northern Expedition, the people in the hometown of the Northern Song Dynasty will certainly respond to the imperial court's call and rise up in succession, and will soon start a prairie fire and attack the State of Jin.

The idea of trying to explore the north in the Southern Song Dynasty has been planned for a long time, and the situation in the Southern Song Dynasty is excellent, which is a mentality of regaining lost ground. In terms of generals, a number of contemporary heroes emerged: Yue Fei, Han Shizhong and Wu Jun.

However, we should know that in this first Northern Expedition, the vast majority of people in the hometown of the Northern Song Dynasty supported the view that the Jin State resisted the "aggression" of the Southern Song Dynasty. This is mainly because the people in ancient China have not yet formed such a profound national concept. Who is not the people as long as they can live and work in peace and contentment?

Moreover, it was chilling enough for the Southern Song Dynasty to hand over the Central Plains to the Jin Dynasty. If the first generation of adherents of the Northern Song Dynasty can still cherish the imperial court's recovery of mountains and rivers, the second generation of adherents, to be honest, have gradually lost their understanding of the Song Dynasty under the rule of the Jin Dynasty, but have more recognition of the Jin Dynasty.

As a result of the first Northern Expedition in Longxing, both countries were indifferent. Although the Southern Song Dynasty saved the situation a little, it changed from the original country of monarch and minister to the country of uncle and nephew, and finally ended in failure. The rulers of the Southern Song Dynasty could sneak back to live a peaceful life, but those who responded to the recovery of lost land in the Southern Song Dynasty and revived the Northern Song Dynasty were greatly influenced. The peace talks between the two countries represent their demise. It is conceivable that the means of treating these people by Jin State is the reason why Bai Xue of the Central Plains is still helping the nomads in the second Northern Expedition.