I think that it's both...
1) There are incidents that just happen...call it "fate", "devine providence", "acts of nature"...whatever belief you ascribe too, it doesn't matter...they are random, unplanned events.
2) By the same token, some events ARE manipulated and planned.
As it relates to history, I think that there are two things that shape it:
1) The "mass acceptance" by a community (scientist, religionist, archeologist, etc.) of what is truly "fact" and
2) The interpretation of those "facts". Let me give you a recent example of what I mean.
100 years from now, if you wanted to read about President William Jefferson Clinton; which would be the more "factual" historical record...the one written by himself in his archives...or the one written by Russ Limbaugh?
What about President George W. Bush...would it be the one from his Presidential archives...or the one written by Michael Moore?
And which historical record would be more "factual"?
History, and mens interpretations of it, can be a real slippery slope...