From Greenbaum and Nelson’s An Introduction to English Grammar (4th edition):
It is normal to arrange the information in our message so that the most important information comes at the end. We follow this principle of end-focus when we put such information at the end of a sentence or clause. In contrast, the beginning of a sentence or clause typically contains information that is general knowledge, or is obvious from the context, or may be assumed as given because it has been mentioned earlier.
If we put a subordinate clause at the end of a sentence, it receives greater emphasis. For example,  emphasizes the action of the committee members, whereas [1a] emphasizes their feelings:
 Although they were not completely happy with it, the committee members adopted her wording of the resolution.
[1a] The committee members adopted her wording of the resolution, although they were not completely happy with it.
Similarly, the pairs that follow show how we can choose which information comes at the end by the way we organize the sentence:
 The American public is not interested in appeasing terrorists.
[2a] Appeasing terrorists does not interest the American public.
 On guard stood a man with a gun in each hand.
[3a] A man with a gun in each hand stood on guard.
 Teenagers are difficult to teach.
[4a] It is difficult to teach teenagers.
Greenbaum, Sidney and Nelson, Gerald. An Introduction to English Grammar. 2nd ed. London, England: Pearson Education, 2002. Print.