The Prince of Qingguo

Modern youth Bai Yuan accidentally travels through time to the crumbling Ji Dynasty, becoming a low-ranking soldier on the frontier. With treacherous officials in court and foreign enemies at the gates, the Central Plains are in turmoil. Armed with cross-era wisdom and a loyal military soul, he forges through flames step by step: purging the army, executing corrupt officials, training a new army, and launching a surprise winter attack on the Northern Desert, stunning the world with a 'Snowy Night Beheading of the Royal Court.' From border soldier to commander, from saddle to dragon throne, he finally leads his black-armored cavalry into the capital, sword pointed at the corrupt court. But the northern expedition has just begun, and hidden conspiracies and catastrophes loom with the sound of hooves... — Description from novelcodex.org