What does Cassius foreshadow to be the outcome of the war?

In short, Brutus's defeat and death is foreshadowed by the appearance of the ghost, which tells Brutus that "thou shalt see me at Philippi." Many theatergoers in Shakespeare's time would have known that Brutus was doomed to die for his role in the assassination of Caesar, and that his death would have occurred at Philippi (which Brutus has already mentioned as the place where their army is going). So when Caesar's ghost, which describes itself as "thy evil spirit," tells Brutus that it will visit him again at Philippi, it is fairly clear that he is predicting his death. However, much like in Macbeth, the appearance of a ghost is used by Shakespeare to suggest that Brutus is experiencing pangs of regret and remorse for murdering Caesar. The ghost is a manifestation of his guilt, and of his growing sense that his evil deeds will revisit him. The fact that none of his sleeping lieutenants see the ghost and that the ghost calls itself Brutus's own "evil spirit" reinforces the idea that it is perhaps a figment of Brutus's own conscience and his sense that things are not, to say the least, going to end well for him.