Polania is a fast-paced faction, which focuses on controlling the early game stages with high range infantry to get a lead and ending the game faster or pressuring the enemy so that he can't recover.
Saxony is the faction with the best defensive options. They possess mechs with high range and damage as well as several mechs with good durability, which gives them the chance of blocking ways and objectives.
Rusviet represents a fast and mobile faction that mainly focuses on closer range tactics. Most of their units are quite fast or got some form of mobility, which makes them great at launching big attacks to breach enemy lines.
Usonia is the first new added faction in Iron Harvest. Their gameplay is all about air supremacy, which they achieve by being the only faction with individual aircrafts.