Why were the Spartans so cruel?

Ancient Sparta was a state with the most cruel traditions and customs. The people of Sparta were the most severe and ascetic for their time. Occupying a small territory, the Spartans created an excellent army that could withstand armies far outnumbered. The Spartans did not build fortresses, barrage ramparts and retaining walls. They believed that they could independently cope with the enemy without any fortifications. From an early age, boys were accustomed to severe trials, instilling in them cruelty, courage and the desire to win. The Spartans simply killed sick children. Spartan society was healthy, strong and violent.