Just the quick History for those who are lost:
381 AD - Constantinople 1 set in place the Nicene Creed without the filioque
435 AD - Council of Ephesus confirmed the creed and proclaimed anatemas on additions to or subtractions from the Creed
451 AD - Council of Chalcedon confirmed the Creed and the Anathemas.
589 AD - Third Council of Toledo did not change the Creed but did specify that the Nicene Creed should be said or sung in the liturgy for Sundays and Holy Days.
Somewhere in the blurry bit the filioque appeared in Ibera and Gaul, and then Germany.
794 AD - Council of Frankfurt authorised it's inclusion under Charlmagne without Papal assent.
809 AD - Council at Aix-la-Chapelle (Charlemagne again) asked the Pope if they might include it and he said no.
847 AD - Monks in Jerusalem disagreed with it's use and the Pope forbade it.
1014 AD - Benedict IX acquiesced to a request from Henry II (HRE) and Michael 1 Cellairis objected. The East argued it was the Creed of the Councils, and the West argued that he held the Keys of the Kingdom.
1054 AD - Mutual Excommunications East and West not liften till after Vatican 2.
A Quick note on Procession
John 14:15-17
John 15:25-27
John 20:20-23
These are the three key texts. At issue is that the East argue that origins always lie ultimately in the Father. The only viable way to read the filioque is 'from the Father through the Son' otherwise wyou will do damage to one of the Johannine texts.
So at the heart of the Great Schism is Procedure, Procession, and Primacy.
Hope that helps