When nations are violently threatened, the choices that they make in order to cope with the challenge of war reflect different alternative possible reactions. They may choose to fiercely fight their battles; they may prefer to surrender, and sometimes the options lay in-between. One puzzle is, therefore, what makes nations fight, and more importantly-what causes them eventually to win or to lose the war. In search for an answer, this study inquires through secondary sources three historical case studies from World War II: Britain, France and Germany, and reviews how each of these major European powers acted throughout the war. After each historical description, the study examines the part that national ethos played in the manner in which each state handled war in moments of crisis. The national ethos of a people is the creed formed from the shared values and traditions through which the nation views its past, present and future; it is the integrating element that defines a nation's identity and bonds it into a coherent social group. The study reveals how national ethos is intertwined with another phenomenon of social psychology that turns it into a crucial factor in the management of international campaigns: war enthusiasm. Since national ethos is so crucial for the results of the war that a country might lead in order to survive or prosper, it is imperative for decision makers to bear in mind that it is also subject to a process of shaping and reshaping, as the Soviets have proved in relation to their Russian national ethos during World War II. A word of caution, however, is noteworthy: a wide historical perspective shows that even though the right kind of national ethos is essential for winning a war it is far from being enough. Hence national ethos proves, at the end of the day, to be a necessary condition for military victory but certainly not a sufficient one.