The 300 were able to defeat hugely superior numbers due to a combination of factors: they WERE superb soldiers and they had a fanatical tradition of fierceness and courage in the face of any foe. Finally, and perhaps most important, they defended a pass so narrow that it was impossible for the Persian forces to concentrate sufficient troops to overwhelm the 300. In the age of the sword and spear, your attack is only as good as the number of points you can present directly at enemy flesh. If the gap could be filled by a hundred men, the Persians could only face them with a hundred men at a time.
The 300 were able to defeat hugely superior numbers due to a combination of factors: they WERE superb soldiers and they had a fanatical tradition of fierceness and courage in the face of any foe. Finally, and perhaps most important, they defended a pass so narrow that it was impossible for the Persian forces to concentrate sufficient troops to overwhelm the 300. In the age of the sword and spear, your attack is only as good as the number of points you can present directly at enemy flesh. If the gap could be filled by a hundred men, the Persians could only face them with a hundred men at a time.
Honestly, ancient history relies upon the accuracy of a very limited number of historians. Is Herodotos the only historian who wrote about this battle? I take all ancient history with a grain of salt- it may or may not be true.