JAMIE MCINTYRE:

Each leg of the triad has its advantages. Submarines are stealthy, virtually undetectable, and therefore nearly invulnerable.

Bombers are slow enough to be recalled at the last minute. It's the third leg, the intercontinental ballistic missiles, on hair-trigger alert, that are under the microscope.

We're flying over the missile field that essentially surrounds Minot Air Force Base, 150 ICBMs buried in silos underground spread across 8,500 square miles of North Dakota.

It's just one of three missile fields that cover five states, Montana, Wyoming, Nebraska, Colorado, and North Dakota, 450 ICBMs altogether. Were it not for the security fence, this silo would be barely visible in the snow. But the locals know where it is, and so do America's enemies.

Having so many missiles in fixed, known locations makes them a tempting target if an adversary were to contemplate a first strike, which in turn, critics argue, creates pressure to launch right away, at the first sign of attack.

Among those critics, no less than former U.S. Strategic Commander General James Cartwright.

GEN. JAMES CARTWRIGHT (RET.), Former U.S. Strategic Commander: You have automatically forced the president, in our case, to make a decision to use his weapons or lose them. That doesn't make a lot of sense. Use or lose doesn't contribute to deterrence.