The different liturgical traditions with regard to the Creed came into contact with each other in early-ninth-century Jerusalem.
Western monks, using the Latin Creed with the added Filioque, were denounced by their Eastern brethren. Writing to Pope Leo III for guidance, in 808, the Western monks referred to the practice in Charlemagne’s chapel in Aachen as their model. Pope Leo responded with a letter to “all the churches of the East” in which he declared his personal belief that the Holy Spirit proceeds eternally from the Father and the Son. In that response, the Pope did not distinguish between his personal understanding and the issue of the legitimacy of the addition to the Creed, although he would later resist the addition in liturgies celebrated at Rome.
Taking up the issue of the Jerusalem controversy, Charlemagne asked Theodulf of Orleans, the principal author of the Libri Carolini, to write a defense of the use of the word Filioque. Appearing in 809, De Spiritu Sancto of Theodulf was essentially a compilation of patristic citations supporting the theology of the Filioque. With this text in hand, Charlemagne convened a council in Aachen in 809-810 to affirm the doctrine of the Spirit’s proceeding from the Father and the Son, which had been questioned by Greek theologians. Following this council,
Charlemagne sought Pope Leo’s approval of the use of the creed with the Filioque (Mansi 14.23-76). A meeting between the Pope and a delegation from Charlemagne’s council took place in Rome in 810. While Leo III affirmed the orthodoxy of the term Filioque, and approved its use in catechesis and personal professions of faith, he explicitly disapproved its inclusion in the text of the Creed of 381, since the Fathers of that Council - who were, he observes, no less inspired by the Holy Spirit than the bishops who had gathered at Aachen - had chosen not to include it. Pope Leo stipulated that the use of the Creed in the celebration of the Eucharist was permissible, but not required, and urged that in the interest of preventing scandal it would be better if the Carolingian court refrained from including it in the liturgy. Around this time, according to the Liber Pontificalis, the Pope had two heavy silver shields made and displayed in St. Peter’s, containing the original text of the Creed of 381 in both Greek and Latin. …
Source:
http://www.usccb.org/beliefs-and-te...ox/filioque-church-dividing-issue-english.cfm