Taking an ancient western history class we learned about sea people that invaded the Egyptians. Who were they and where did they come from? How did they manage to take down a civilization as big as Egypt without writing down some form of history?
I can enlighten you on this subject.
The Sea Peoples were actually several groups of people, including the Sherden, Peleset, Denyen, Lukka, Shekelesh, and others. Their origins are slightly mysterious, as we don't have a specific place we can tie them to, though most scholars put their origins in the Aegean
One group of the Sea Peoples that you might be familiar with are the Philistines of the Old Testament (you know, David and Goliath). These are almost certainly identified as the Peleset.
I have spent many years excavating Philistine remains in Israel, and I can tell you that they are clearly a foreign group to the region of Israel, and most likely were from the Aegean area, possibly Greece or one of the many islands between Greece and Turkey. We have not been able to get more specific than that. Their pottery closely resembles Mycenean pottery from one of the major Greek city-states of the time (referred to as Myc IIIc), and they have other quite Aegean features in their material culture such as square hearths, and their architecture is laid out in quite a foreign fashion.
They were accomplished seafarers, according to many illustrations of them by the Egyptians and by themselves. However, though they have left symbols, we have not been able to decipher any of their writing, so we do not have their side of the story. At this period of time, the only true, deciphered writing systems in the Ancient Near East were in Egypt (hieroglyphs) and Mesopotamia (cuneiform). Writing was just beginning to catch on in the areas in between. So that's why they did not leave any writing.
As for the battle with Egypt, it is memorialized in the funerary reliefs at Medinet Habu, where massive wall murals depict the sea peoples battling the Egyptians.
To be honest with you, while most scholars believe that Egypt took a major hit in that battle, some are now suggesting based on very recent evidence that they had significant influence on early Philistine settlements that the Egyptians won that battle. Egypt was not the same afterwards, it is true, but the Sea Peoples were defeated after ravaging the land from Turkey all the way down the coast.
Egypt continued to be a power, but they were not as strong, due to the many losses from the battle. They were not "taken down", but rather they won an extremely hard-fought battle.
Here are some sources for further reading on the Philistines
This wikipedia article is pretty well-researched and will give you an overview of everything.
This is the overview site report for the site of Ashkelon, likely the first Philistine settlement and one of their major strongholds in Israel.
Betancourt, Philip P. "The Aegean and the origin of the Sea Peoples." The Sea Peoples and their world: a reassessment (2000): 297-303.. I linked to this book earlier, but this is a specific chapter about their origins.
If you have any questions whatsoever, or if I have been unclear in my answer, please let me know and I will do my best to fill in the details.
EDIT: formatting