Mosquitos as decisive

Every blind man seems to want his piece of the elephant to be the determinant component. One gets worn down reading that the [fill in the blank] was the decision point for the war. Now, make way for the lowly mosquito:
Bell argues, convincingly, that the spread of malaria and yellow fever throughout the South affected the choices military leaders made and the outcome of battles.
A good thing can be ruined by hype.