Summon the Fourth Natural Disaster, the Northern Expedition!

As a time traveler, Qin Xuan was involved in the ruthless battle for the throne. When he cut off the head of the eldest prince and seized the throne. However, the Northern Barbarians ambush the general until he died. Occupied a large area of land in Xuan Kingdom... The high-end combat power is not as good as that of the enemy, and the number of soldiers is not as good as that of the enemy. How can we save the situation? The system came, and when he learned that the system could summon players... Northern Expedition!