High Defense, Strength, and Health
The Soldier is a blunt force instrument of war. His high health, and quick reflexes make him a master of hand to hand combat.
He starts with heavy armor and a spear - which perfectly suits him to be running interference on the front lines, while your Mages and Archers do their damage at distance.
You always need a heavy in your group. The Soldier is a good option to start with if you plan on recruiting an Archer or Mage that can attack at distance along the way...