Since the very dawn of time people have ebbed and flowed through the mouth of Cork harbour with the rising and the falling of the tide. Being isolated from Europe brought us to the attention of merchants, raiders, armies and navies, indeed there are recorded histories going back over 2000 years telling us of trade with Phoenician merchants from the eastern Mediterranean.
St Patrick and the coming of Christianity seemed to coincide with our increased skill as gold and bronze smiths which eventually lured the dreaded Norsemen and Vikings who raided and pillaged all they could see, before they finally settled down and found themselves nice Irish girls!
This essentially set the scene for the next 1500 years of foreigners arrive, locals try and throw them out, bigger army comes back locals run for the hills. Big army settles down, locals come down from the hills and try to push them back out again.
Throw in plague, famine, rebellion and lots of emigration and you get a general picture of Irish history. Then remember that Cork has the biggest harbour in Ireland (second biggest in the World) and so, 2000 years of everything significant that has happened in Ireland has more or less had some connection with the area.