Kirk : "Bones, do you remember the 20th century brush wars on the Asian continent? Two giant powers involved, much like the Klingons and ourselves. Neither side could pull out."TOS : A Private Little War
McCoy : "Yes. It went on bloody year after bloody year!"
Kirk : "What would you have suggested, that one side arm its friends with an overpowering weapon? Mankind would never have lived to travel space if they had! No. The only solution is what happened back then. Balance of power."
McCoy : "And if the Klingons give their side even more?"
Kirk : "Then we arm our side with exactly that much more. A balance of power, the trickiest, most difficult, dirtiest game of them all. But the only one that preserves both sides."