Celtic Invasions The Celtic way of life reflects the essence of a real world and a real people. Feasting, fighting and ritual boasting were typical of the Celts, who were an ancient people who controlled much of Europe and the British Isles for about 800 years. Though their world is now dead, their culture influenced a good part of the European Continent, and spread all the way from Ireland to the shores of the Black Sea. The Celt’s barbarian like battle tactics determined their overall influence in European history. The customs, history and culture of the people involved in the Celtic invasions were what determined the cause and outcome of the great conflict. The Celts were a