The Beginning of Sparta In about 100 BCE, the Dorians invaded Greece from the North. During the Dark Ages, the Dorians made their way south, capturing the inhabitants of the lands they passed through as helots. At the beginning of the Dark Ages, it is thought that there were many Dorian settlements in Laconia, each with their own helot population. At some time during the Dark Ages, Sparta overtook these fellow Dorian settlements and their helot populations, as well as control of the whole of Laconia. The Spartans kept the helots as a huge, strong slave race and, although they...
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Review of Sources

It was very difficult to find the relevant parts of each ancient source, because these books were written to be read as stories or poems, rather than books of non-fiction used for research. I consulted Life of Lycurgus by Plutarch, The Histories by Herodotus and Constitution of the Spartans" by Xenaphon.

It is very hard for modern historians to use ancient sources, though, because the stories can often be biased and could even be used as propaganda, especially when Sparta is involved, because they were well known for influencing literature that their enemies could read.