People don't need to work outside: people don't need to take on extra labor.
Simple service: it reflects social stability, and military service, corvee and taxes are relatively light.
Self-protection, many benefits: it shows that there were abundant products and sufficient food at that time.
The meaning of the whole paragraph: there was no military service abroad, and the people did not need to bear extra labor, reflecting social stability. Military service, corvee and taxes were very light, indicating that there were abundant products and food at that time.