Travel through the early Tang Dynasty and take over the dilapidated Sishui Castle.
They were short of food and had few soldiers, and they were surrounded by powerful enemies who were pressing every step of the way.
Proficient in ancient blacksmithing, he makes batches of standard steel knives and personal mail armor, and relies on ordnance to build an elite army.
Accommodate refugees, build cities and expand land, and grow in power step by step.
All the talented people in the world defected to Li Tang, but I was the only one to seize control of Sishui and secretly intercept the national destiny of the Tang Dynasty.
After a head-on confrontation with Li Shimin at Hulao Pass, a fortress master bucked the trend and rewrote the troubled times!
[Alternate history, has nothing to do with official history]