During previous centuries, political leaders (seemingly) didn't use ideology as a justification for conflict, but in the 20th century almost every conflict was ideological in nature. How true is that statement? If it is true, was it due to increases in mass media and the incorporation of the masses into the political sphere? If false, is the perception that it was an ideological century due to the increased propaganda activities of 20th century governments or our nearness to it time-wise?
Mark Mazower, professor at Columbia University, posits the history of Europe during the twentieth century as just that: a struggle between competing ideologies. This was not the result of increased government propaganda, but, according to Mazower's model, a result of the large-scale organization of the masses that occurred in the twentieth century but not before that. In particular, Mazower argues that ideologies rose as a central component of European identity during the interwar period--the horrors of the First World War compelled people to embrace the postwar democratic structure as mankind's savior, while the subsequent failures of the liberal democracies necessitated the adoption of new ideologies. Mazower convincingly argues that each of three camps--liberal democracy, communism, and fascism--stood on the precipice of the complete domination of Europe. At the same time, and in defense of his overall thesis, however, Mazower argues that the three ideologies were not so distinct all three, for example, called for some form of eugenics, promoted some form of state interference in the private life of citizens, and, overall, theorized some kind of political and economic plan that could create "their own utopia as the End of History."
In Mazower's story, the first ideology to fall was fascism, which was destroyed and discredited during the Second World War. Thereafter, Europe remained locked in a battle between "democracy" and "communism." Liberal democracy's eventual victory over communism was, as the back cover summarizes, "anything but a foregone conclusion," and thus its value as an inevitable unifying force in Europe should be questioned by those who study history Europe, Mazower argues. Mazower even asserts that his analysis reveals that the unified "Europe" that we study as historians may have never existed at all (which, of course, is not an idea unique to his analysis). He concludes that "if we face the fact that liberal democracy failed between the wars, and if we admit that communism and fascism also formed part of the continent's political heritage, then it is hard to deny that what has shaped Europe in this century is not a gradual convergence of thought and feeling but on the contrary a series of violent clashes between antagonistic New Orders."
If you are interested in reading more about this theory (which, so long as you avoid applying it to modern politics as Mazower wishes you do do, is quite valuable), I have very good news for you:
The book that I've summarized here, Mark Mazower's Dark Continent: Europe's Twentieth Century (1998), is published on a popular press and is thus very cheap. You can find it on Amazon for $.01 plus shipping.