Why Did Leonidas Only Bring 300?

Herodotus tells us that Leonidas, in line with the prophecy, was convinced he was going to certain death since his forces were not adequate for a victory, and so he selected only Spartans with living sons.

Why did Leonidas only bring 300 Spartans?

In the late summer of 480 B.C., Leonidas led an army of 6,000 to 7,000 Greeks from many city-states, including 300 Spartans, in an attempt to prevent the Persians from passing through Thermopylae.

Was there really only 300 Spartans?

In short, not as much as suggested. It is true there were only 300 Spartan soldiers at the battle of Thermopylae but they were not alone, as the Spartans had formed an alliance with other Greek states. It is thought that the number of ancient Greeks was closer to 7,000. The size of the Persian army is disputed.