Throughout the substantial modifications to the relationship between the imperial crown, the German Church, and the secular princes in the twelfth and thirteenth centuries, the German aristocracy continued to cling to conflict as one solution to their complex political needs. In permanent possession of retinues, fortifications, and other resources of war, and continually alert to the necessity of defence against their aggressive neighbours in the regions, the princes turned to violence when other means failed them. This tradition is plain to see in the history of the East Frankish realm of the tenth century. In the eleventh, it is vividly outlined by Wipo in his biography of Conrad II, through Duke Ernest of Swabia's struggles with his neighbours and with the emperor; and by Adam of Bremen in his account of Archbishop Adalbert of Bremen's political ambitions. It reached a new climax in the virulence of the Saxon War and the subsequent War of Investitures. The sources emanating from both sides tend to agree upon the bitterness of these conflicts. The tradition runs on through the wrangles of the twelfth and thirteenth centuries for possession of the crown, for ducal and other titles, and for lands in dispute between the princes themselves. The ascription of violence to the German nobility was a literary commonplace based in part upon a classical model. But Teutonicus furor was sometimes remarked upon by the Germans themselves, and had a realistic function in contributing to princely success and survival. Regional history is punctuated by innumerable wars and rumours of them.