Why did spartans place so much stress on military service?

1. The Spartan were feared that the helots would revolt. 2. Helots were the captured workers who served the Spartan citizens. 3. Spartan boys began military training at age 7, and remained on active duty until age 30.4. Soldiers were encouraged to succeed or die trying. 5. Ultimately, Sparta fell behind science and trade because they only focused on military.