War indeed has its benefits, that's why wars happen. And there are, perhaps what we might call necessary wars, as the above examples about Nazi aggression and the Holocaust indicate. But they also tend to have a negative effect on civil liberties, on workers' rights, on civilian populations in war zones, and in a host of other ways. One post above mentions Israeli additions of formerly "forbidden" territory, and Chilean acquisition of Bolivian land without mentioning that these are clearly not good for the people who had these lands forcibly taken away. Ultimately, war is an exercise of state power. As with any act of power, someone benefits. Whether these benefits outweigh the human lives and treasure expended to achieve them is a much more complicated question.