That's not what I meant. Obviously you need to study the subjects extensively and only then you retain a considerable chunk of the material. But they don't really demand exact dates or things like that. Like if you are discussing Russia Pakistan ties, you can write "on the occasion of Soviet invasion of Afghanistan in the late 1970s." Although this was just too simple an example, yet most of the discussions are generalized, spiced up with specific quotations and references. You can memorize a few of them but the rest of the things are general. At least that's what I have learned from a number of essays flagged as "best essays" or essay of the month and so on.