Kissinger on collective security

“Collective security . . . is a legal construct addressed to no specific contingency. It defines no particular obligations except joint action of some kind when the rules of peaceful international order are violated. In practice, action must be negotiated from case to case . . . . The idea that in such situations countries will identify violations of peace identically and be prepared to act in common against them is belied by the experience of history . . . . An alliance [by contrast] comes about as an agreement on specific facts or expectations. It creates a formal obligation to act in a precise way in defined contingencies. It brings about a strategic obligation fulfillable in an agreed manner. It arises out of a consciousness of shared interests, and the more parallel those interests are, the more cohesive the alliance will be.”