Do any philosophers argue for a state of constant war? Not as a state that needs to be prevented, but an ideal state. I don't think that's Marx, but it may be some variants of Marxism. Does Machiavelli argue for this in some way?
Maybe not what you are looking for...
If our definition of war extends beyond direct military conflict to include conflicts such as the arms race and its doctrine of mutually assured destruction, then military strategists have developed and adopted a philosophy based on mathematical game theory and its concept of Nash equilibrium.
Nash equilibrium has a technical definition which roughly says that given a strategy adopted by one side, neither side could do strictly better (i.e., increase their payoff) by adopting another strategy. This gives rise to an infinite game where it is in the interest of both sides to keep the game going. Particular conflicts, such as direct military conflicts (e.g., Ukraine), may come and go but the game continues indefinitely.