【Three Kingdoms HEROES】There are enemy squads in the Campaign that have 2 generic shieldsmen. How do I get more shieldsmen for my team?

You only get one of each unit (except for elite soldiers).

One way to get multiple shieldsman would be to use various items such as the “Power-up: Shieldsman” and the “Add Shieldsman,” but otherwise you are limited to just one of each unit.