Wales was now surrounded on the land side by a people who spoke strange languages, and who worshipped different gods, for the Angles and the Saxons were heathens. From the sea also it was open to attack. Sometimes the Irish came. But the most feared of all were the Danes, whose sudden appearance and quick movements and desperate onslaughts were the terror of the age. The “black Danes” came from the fords of Norway, the “white Danes” from the plains of Sweden and Denmark. The Danes settled on the south coast: Tenby is a Danish name. Offa, the king of the Mercian Angles, took the rich lands between the Severn and the Wye; but Offa’s Dyke (Clawdd Offa) is probably the work of some earlier people whose history has been lost. It was only by incessant fighting that the enemy could be kept at bay. Of all the kings who tried to defend his country against the enemies which now stood round it, the greatest is Rhodri, called Rhodri Mawr—“the Great.” From 844 to 877, by battles on sea and land, he broke the spell of Danish and Saxon victories; and his might and wisdom enabled him to lead his country in those dark days. Like Alfred of Wessex, who lived at the same time and faced the same task, he stemmed the torrent of Danish invasion and beat the sea-rovers on their own element. Like Alfred, he left warlike children and grandchildren. One of the grandsons was Howel the Good, who put the laws of Wales down in a book. Wales and England were now, both of them in their own way, trying to become one country. It was seen by many that strength and peace were better than division and war. In England, the Earls of Mercia and Wessex tried to rise into supreme power. In Wales Llywelyn ab Seisyll, victorious in many battles and wishing for peace, made the country rich and happy. Still, when he died in 1022, the princes said they would not obey another over-king. But the long ships full of Danes came again; the Angles crossed the Severn: war and misery took the place of peace and plenty. Griffith, the son of Llywelyn, came to renew his father’s work. In the battle of Rhyd y Groes on the Severn, in 1039, he drove the Mercians back; in the battle of Pencader, in 1041, he crushed the opponents of Welsh unity; in 1044 he defeated the sea-rovers at Aber Towy. At the same time Harold, Earl of Wessex, was making himself king of England. A war broke out between Griffith and Harold; and, during it, in 1063, the great Welsh king—“the head and the shield of the Britons”—was slain by traitors.