Both felt hard done by, by previous settlements; the Kaiser felt he had been unfairly ignored in the carving up of Africa, whilst Hitler felt the punitive Peace f Paris settlement was unfair and an humiliation to the country of Germany. It was these feelings that can be seen as one of the reasons for their aggressive foreign policy; the Kaiser wanted to gain for Germany her "place in the sun", an empire which would reflect her (ever increasing) industrial, financial and military might, on the other hand, Hitler's main aim was to overturn the Treaty of Versailles, especially those that limited the freedom of Germany in any way, for example, German re-militarization, and re-occupation of the Rhineland.
Nationalism can be seen as another likeness in the roots of the two wars. Nationalism, that originated from the success of German and Italian unification, can be seen as a major contribution to the outbreak of WWI in the context of both long and short term causes. It was nationalism that created a climate in which all the European powers were rivals to each other. This was in reality the biggest underlying cause because without this rivalry, there would have been less of the aggressive foreign policy that was common to so many countries (Germany) and can be seen in itself as a causes for war. Furthermore, such an alliance system that was created wouldn't have existed because the need for collective defence wouldn't have been an issue. Also without the rivalry there would have been little need to maintain peace. Without this rivalry there would have been less imperialism and consequently less militarism. Nationalism was a major underlying cause purely because from this general sentiment developed so many attitudes and actions that many felt a solution of a practical nature was necessary. One of Hitler's main aim's was to overturn the Treaty of Versailles, he saw this as an embarrassment to his country, underlining the concept of the November criminals and appealing to the nationalistic sentiments of his people in his desire to make Germany great.