Brian devoted himself to the development of the industries, the encouragement of agriculture, and the education of the people. He made wise laws and enforced them with justice. He founded schools and colleges. He encouraged art and science, he built roads in every direction, and he gave the distracted country the blessings of peace and prosperity. Instead of fighting among themselves, the people gave their attention to farming, cattle-breeding, trade and manufacturing, literature and the polite arts, and the historians say that another twenty years of Brian's reign would have changed the entire history of the country. Rare Tom Moore has given us a picture of Ireland in those days, when, according to his verses, a beautiful young lady, "Rich and rare were the gems she wore," traversed the entire country, from north to south and from east to west, without being molested.
When Brian became an old man, Mailmora, king of Leinster, conspired with the Danes, the Manxmen, the chiefs of the Orkneys, and the Scots to overthrow him. Sigtryg of the Silken Beard arranged with them to consolidate their forces to overcome the Irish. Sigurd, Earl of Orkney, brought an army ten thousand strong. Broder, the great Viking of the Isle of Man, brought a fleet of two hundred ships and ten thousand men, covered with mail from head to foot, to meet the Irish, who always fought in tunics. Broder had once been a Christian, but had fallen from grace. He was the tallest and the strongest man of his time. His hair was so long that he had to tuck it under his belt. He wore a coat of mail "on which no steele could bite," and he had "no reverence for God or for man, for church or sanctuary."
The venerable Brian Boru, then seventy-three years of age, was camped in what is now Phoenix Park, surrounded by twenty thousand warriors representing the different Irish clans. His sons prevailed upon him not to engage in the battle, and he gave the command to his son Morrough. But he led the column to the Hill of Clontarf on the morning of Good Friday, and when the invaders were in plain sight Brian Boru, holding aloft a crucifix, rode from rank to rank reminding his men that on that day their Lord had died for them, and exhorting them to smite the heathen hip and thigh for their religion and their homes. Then, giving the signal for the onset, he withdrew to his tent at the top of the hill, where he could observe the conflict.