Explain the connection between nationalism, ethnicity and war.
From class, we learned that nationalism and ethnicity appear to be important causes of many internal and international conflicts since 1945. Moreover, the data provided from the web site, www.systemicpeace.org, show ethnic conflicts steadily rising from 1945, peaking around 1991-92, and then slowly declining and leveling off since 1995. I'm trying to wade through the various theories we have learned in my class (which is an undergraduate course on the theories of international relations) in order to adquately explain and answer this question. We read Lake and Rothchild's article "Containing Fear: The Origins and Managment of Ethnic Conflict" as well as Kaufmann's "Possible and Impossible Solutions to Ethnic Civil Wars" in preparation for this article. To make things worse, my teacher doesn't subscribe to any metatheories; he prefers mid-range theories to explain individual phenomena. Again, that is fine, but it makes things very difficult to understand in my class.
When I first read your question, I thought it was a general question regarding World War I! The relation between Nationalism, Ethnicity, and War have been very well studied for that time; if what happened during the First World War is applicable to today, there's some comparisons that can be examined.
The desire for various suppressed ethnic groups to be politically autonomous transcends any specific time; it's interesting that the Balkan conflicts in the 1990's were once again manifesting themselves after nearly a century of suppression. Ironically, it was this same conflict that resulted in all of Europe being at war in the early 1900's. I wonder if the levelling off you state occurring around 1995 was due to that area resolving these long held conflicts.
Perhaps the metatheory you're looking for falls into the realm of philosophy, but could be construed as an "historic axiom:"
"Suppressed ethnic groups are willing to go to war to form their own nation."
You could even consider the Rebellion in the US during the 1860's to fall under this process.
Why there is less "ethnic" war may be due to the efforts of an honest diplomacy developing viable political solutions.