Fortinbras on the move?

Fortinbras has over two thousand soldiers on the move. He says its for a small patch of land in Poland. Yet if it is so small, why is it really needed for him? There's more to it than that, I think. Hopefully Fortinbras isn't going to try and take advantage of the turmoil at Elsinore to take revenge for his father's death. As I am sure he has heard atleast rumors of the going ons at the castle if I heard of them in France.