It was regarded as justifiable war, because it was fought to recapture the places sacred to Christians. Charlemagne he made his wars of aggression definitely religious wars. All the world of north-western Europe, which is now Great Britain, France, Germany, Denmark, and Norway and Sweden, was in the ninth century an arena of bitter conflict between the old faith and the new. Nations were converted to Christianity by the sword just like Islam in Arabia, Central Asia, and Africa had converted whole nations a century ago. With his sword Charlemagne preached the Gospel of the cross to the Saxons, Bohemians, and as far as the Danube which is now Hungary. As the Christian propaganda of Charlemagne swept towards the shores of the north and Baltic Seas, the pagans were driven to sea. They retaliated for the Christian persecutions with plundering raids and expeditions against Christian England .
Ireland has had a history of religious conflicts the I.R.A. (Irish Republican Army) .
against the Protestants. In 1829 Catholics were not suitable for schools throughout Ireland they were only suitable for Protestants. The Catholic peasantry were still called on to pay tithes, and they continued to be harassed by the exactions of tithe-proctors and others, who if the money was not forthcoming, seized the poor peoples cows, furniture, beds, blankets, kettles, or anything they could lay their hands on (History Of Nations 12 Ireland-Scotland p.224).The Catholics were a minority in Ireland much like in the history of Quebec where the English conquered the French, the French were considered lower forms of humans they weren't up to English standards. As the years past the Catholics started to get back at the Protestants forming the I.R.A. I.R.A. and Protestant killings continued into the early 1900s, Britain began launching multi party- talks with the goal of forging a new assembly for northern Ireland and new relations between the north and Irish republic.