Border Soldier: Create Ice at the Beginning, the Barbarians Are Confused

In the third year of Jingde's reign during the Great Yan period, July was extremely hot. The Tuoba barbarians' 30,000 cavalry knocked on the pass, and the remaining 3,000 soldiers of Zhenbeiguan were trapped in the isolated city. Reinforcements were far away. Natsuki, a military boy who had just joined the army for three months, was hit by a stray arrow during the enemy's first attack on the camp - and when he opened his eyes again, he was transformed into a chemical plant technician of the 21st century. There is no system, no magical skills, just a brain of modern knowledge. Using saltpeter to make ice prevented the frontier troops from falling down due to heat stroke in the scorching summer; improving the crossbow machine, which directly doubled the range; clearing the battlefield to snatch the wounded soldiers back from the hands of the King of Hell; blasting the tunnels to collapse the enemy's siege tower. From a small soldier who could be filled in trenches at any time, to a captain, to a captain, to a general, to the Marquis of Zhenbei—— Barbarian cavalry? In the face of absolute technological crushing, they are just a bunch of heads to be harvested. I will guard the northern gate of Great Yan.