Why did the Spartans not help the Ionians against the Persians?

Answer 1

The Ionians revolted in 499 BCE. Eretria and Athens sent military forces to help them because they were Ionians, and some of the cities had been their colonies, so the felt an obligation to help. Sparta and other southern Greek cities were mainly Dorians and felt no such obligation, however the Athens-Eretria intrusion convinced the Persians that all the Greek cities had to be brought under control, and in 480 BCE the Persians invaded mainland Greece.

The Spartans led the successful resistance to this two year invasion, however the Spartans could see that the Greek city-states in Asia Minor would be under perpetual threat from the Persians and produced a plan to evacuate them and resettle them in mainland Greece, so avoiding ongoing conflict.

The Athenians had a different idea and formed the Delian League to protect these Asian cities, and warfare went on for another 30 years.

The Spartans, always looking for peaceful settlement of problems, walked away from this ongoing war, particularly as they had problems at home with their own rebellious serf population.

As a footnote, the Spartan approach was eventually adopted over two millennia later after World War 1 was over. The Greeks fought a war in western Turkey to hold territory there with a mainly Greek population. They lost and evacuated the Greek people back to the mainland. The Spartans had had it right 2,400 years earlier.