You are asking an incredibly broad question about an entire style of warfare as it developed through time, and I don't think I could even approach a satisfactory answer. I would recommend as a primer though Max Boots "Invisible Armies". While I felt his book lacked much in the way of in-depth analysis, it does provide an over view of notable guerrilla campaigns through history, so there are much worse places you could start than his book.

I agree with the fact that guerilla warfare has existed since warfare has because of the difficulty off getting accounts of ancient guerilla warfare. However, there is one form of ancient guerilla warfare I do know a fair amount about, ancient Spartan guerilla warfare. The guerilla warfare training of an ancient Spartan male starts in their teenage years around age fifteen in the Spartan education system setup by their constitutional reformer, Lycurgus, called the agoge. Young Spartan males participated in guerrilla warfare secretly for years in the countryside of Laconia and Messenia to keep down the helot population down. They had to participate in this secret guerilla warfare service called the Crypteia to control the 10:1 slave population and to get the approved training necessary to appease their educational mentors, the paidonomos. This was a type of training that came in handy during the days before the battle of Thermopylae in 480 B.C. and during the Sicilian Expedition in 415-413 B.C., a crucial campaign in the Peloponnesian War between Athens and Sparta.

Diodorus Siculus accounts for the use of Spartan guerilla warfare in Book V of his Bibliotheca Historica (or Universal History) when he talks about a Spartan night raid on Persian King Xerxes’ camp days before the famous battle of Thermopylae. It was a use of guerilla warfare that allowed a small Spartan raiding party to kill many soldiers and officers that were in their sleep. And it only ended because the officers around Xerxes’ tent woke up and once the Spartans noticed this, they retreated back to their own camp.

The next time Spartan guerilla warfare came in handy was against the Athenains, led by General Nicias, in the Sicilian expedition. Spartan guerilla warfare is documented in Thucydides’ The Peloponnesian War in his sixth and seventh book when the Spartan General, Gylippus, helps their ally Syracuse repel an Athenian invasion on the island of Sicily. Through the use of guerilla warfare tactics at night, Gylippus and his fellow Spartan hoplites took the Athenian forts at Labdalum, Plemmyrium and Epipolae. The seizing of these hilltop forts by night ultimately brought about the defeat the Athenian army at the Assinarus River, a massacre that also took place at night.

It is clear that the use of night time attacks with small raiding parties and guerilla warfare was used regularly by the Spartans but there is very few documentation of this Spartan practice. Due to fact that the Spartans were so good at guerilla warfare and killed their victims that would likely write about it. This is an important distinction to acknowledge because the Spartans did not write about war as much as other ancient Greeks did. So it is only the accounts of ancient Greek authors of Diodorus Siculus, Thucydides, Plutarch’s On Sparta, and Xenophon in his Constitution of the Lacedemonians that speak of the ancient Spartan guerilla tactics. Although there are only a few accounts, it should be known that the Spartans were an ancient race of people that used guerilla warfare regularly after they conquered their Messenia neighbors in 668 B.C.

Sources:

Diodorus Siculus Bibliotheca Historica

Thucydides The History of the Peloponnesian War

Xenophon Constitution of the Lacedemonians

Plutarch On Sparta

Jean Ducat. Spartan Education. Translated by Emma Stafford, P.J Shaw and Anton Powell. Swansea: The Classical Press of Wales, 2006.

Nigel M. Kennell. The Gymnasium of Virtue: Education & Culture in Ancient Sparta. Chapel Hill, NC: The University of North Carolina Press, 1995.