Guy was involved in the war between King Philip II Augustus of France and the English ruler of the "Angevin Empire", Richard the Lionheart.
When the King invaded Auvergne and laid siege to Issoire, Guy and his cousin, the Dauphin Robert, called on Richard the Lionheart for help.
In contrast to him, his brother, Bishop Robert of Clermont, supported the King, from whom he hoped to strengthen the episcopal position against the count's.
Only his son received a significantly reduced part of the Auvergne back, the rest remained in the possession of the French Crown as Terre Royale d'Auvergne.
According to the "Canso de la Crozada" by William of Tudela, Guy led the first military actions of the Albigensian Crusade in May 1209.
Together with the Viscount of Turenne, the Archbishop of Bordeaux and the Bishops of Limoges, Agen and Cahors, he led a crusader army into the Quercy region, which belonged to Raymond VI, Count of Toulouse, who was exiled at the time.