The dictatorial, paranoid regime of North Korea is known for issuing bellicose threats that it will annihilate its enemies, but in the spring of 2013, those admonitions started to seem shriller than usual. North Korea's government-controlled news media announced that dictator Kim Jong Un had ordered his military to put its missiles on standby for a possible strike against U.S. military bases in South Korea, Hawaii and Guam, and even the U.S. mainland. One North Korean newspaper proclaimed that San Diego, Austin and Washington, D.C. were potential targets [source: Cha].

Those might seem like big words, coming from a small, isolated country on the other side of the world. But in the U.S., officials didn't just brush it off as bluster. That's because they knew that the U.S. Defense Intelligence Agency (DIA), the Pentagon's own spy service, had just concluded with "moderate confidence" that the North Koreans actually had reached the level of technological sophistication needed to launch ballistic missiles armed with nuclear warheads. However, the missiles were thought to be less than reliable, and DIA believed they didn't yet have the ability to reach U.S. cities [source: Alexander].

Even so, the Pentagon subsequently warned in a report to Congress, North Korea was on the way to eventually being able to build an intercontinental ballistic missile (ICBM) capable of reaching the U.S. [source: Alexander]. And U.S. territory and bases in the Pacific—and its ally, South Korea — already were at risk.

But as the world watched anxiously, one important man was markedly calm. In testimony to the U.S. Senate, Adm. Sam Locklear, head of the U.S. Pacific Command, said that the U.S. was prepared to intercept North Korean missiles and prevent them from reaching their targets. "I believe we have a credible ability to defend the homeland, to defend Hawaii, defend Guam, to defend our forward-deployed forces and defend our allies," he said [source: Miklaszewski and Kube].

Locklear's seeming confidence was reassuring. Or was it? How exactly would the U.S. military intercept a nuclear missile aimed at Americans? And how dependable are the antimissile defenses, upon which the U.S. has spent $90 billion since 2002 [source: Masters and Bruno]?