I had to do an essay for a module of mine about Modern Europe, and the question I picked to do it on was the Cold War entitled "Why Did the Cold War last as long as it did?". I thought it would be interesting to look at presidential elections and transfers of power between Russian leaders and why that kept passing power over to Cold War hawks or at least people who couldn't . However, I was worried that wouldn't quite fly with my tutor (who grades the essays), so I asked her if I could focus on that one particular area of the Cold War and politics of the Cold War and she said I could, that I just need to make it explicit that I was focusing on that one area. So I wrote that essay, making sure I spelled out what I was looking at, and that I was focusing on a particular area.
I ended up getting a D-, and the main reason for it was because "While the role of leaders in the US and Russia are a contributing factor to the length of the Cold War, it is not the only factor. In order to analyse the essay question to its full potential, you need to address a number of other issues, such as politics (esp post WWII), economies (eg Marshall Plan) the Communist-Capitalist division/tension, nuclear arms race, space race, and economics - one reason is not really sufficient." The essay is worth 40% of my final grade for this module.