An alliance defense must be effective and credible, and failing to tend to these requirements risks undermining not only an individual alliance but related ones, and even the broader anti-hegemonic effort. Stretched too far, an alliance network can weaken and even break. This was a problem with the Pactomania of the 1950s, which helped lead the United States into the agonizing Vietnam War and threatened to impair, if not collapse, its whole Cold War effort.13
