Why is history considered a science and art?

First of all History is always writen by the winner , then later revised as threw time more information is uncuverd and the puzzel start. As many documents can be interpreted many ways so can history for what the intentions of a person or country wher after they have bean recovered from the ashes ,then lies in the eye of the beholder! The art of putting it all together before time swallows the truth. The science of pruving that your take on past events is the correct one! B.L.Laschinsky Germany