This is a very interesting and truly compelling question. While there are several items that can hope to explain the aggressiveness of the powers that will come to be known as the Axis powers, I am going to try to frame all of them into one dimension that has multiple components. I think that the major factor that underscored the aggressiveness of each foreign policy was the charismatic effect of each nation's leader. Each of these nations' leaders- Tojo for Japan, Mussolini in Italy, and Hitler in Germany- came to ascend power by personifying themselves as the nation. They were willing participants to market their own senses of self as embodiments of their nations, making them appealing to their citizenry, and invoking the sensibility that their nations' exceptionalism justified aggressiveness in foreign policy. Each of these leaders were charismatic enough to be able to inject themselves into the nation, as a whole. Hitler's ascendancy to power was rooted in the notion that Germany has been wronged by the Treaty of Versailles, and that the glory of German nationalism awaited, and he was the vehicle to bring this vision into reality. Mussolini was the first of the three leaders to do the same as Hitler, in terms of identifying himself as the embodiment of Italian exceptionalism and glory. Tojo was able to convince the Japanese citizenry that the rising and setting of the sun lay with Japan. Each leader "became" their nation, and in this process, invoked a sense of nationalism to inspire their nations to pursue aggressive policies in terms of their relations with other nations. They suggested that the vision that each leader had for each nation, this notion of national exceptionalism, must be spread over as much land and territory as possible. In this invocation and in the convincing their citizens that they were the only ones fit to accomplish this task, allowed them to pursue aggressive and confrontational foreign policies.