You win when you completely destroy your enemy a la Germany and Japan in WW2. Anything other than that is a loss.
I agree.
At one point, the thinking was that war was a little like chess -- if you capture the enemy's capitol (checkmate the king) then you win the war.
A little later, the thinking was that if you destroy the enemy army, you win the war.
In WWII, the idea was to completely destroy your enemy.
As this article indicates, the more recent idea is to make the enemy civilians love you more than they love their own government or their own religion. This just fails.
I believe that destroying the enemy and intentionally causing massive casualties is really the only viable strategy. Historically, this works very well.