The Pentagon is facing its worst cash crunch in more than a decade, with potential cuts of up to a half-trillion dollars over the next decade if Congress doesn't act soon. Yet the U.S. military still somehow found the money on Tuesday to put a down payment on a $10 billion upgrade of its nuclear weapons in Europe – y'know, just in case there's another Cold War.

The $178 million, three-year contract with Boeing is for a prototype "tail kit" for the B61 nuclear weapon. The fins and control systems will be similar to the ones on today's conventional, GPS-guided bombs, potentially making this enhanced version of the B61 the most accurate weapon of mass destruction ever. It's one part of a bigger package of improvements to the B61 that the Pentagon insists it needs in order to keep this slice of its nuclear arsenal ready for war, if needed. Everything from the spin rocket motors to the electronic neutron generators will be refreshed. Total cost: an estimated $10 billion.

Just about the only thing that won't change is the weapon's nuclear "pit," and who the U.S. military plans on dropping the thing on. "Who's the target? The Red Army. The Red Army that's sitting in East Germany, ready to plunge into Europe," explains. Jeffrey Lewis, a nuclear weapons expert at the James Martin Center for Nonproliferation Studies. "No, I'm serious."

The U.S. has other, bunker-busting nuclear weapons that might be employed if, God forbid, there was ever an atomic showdown with North Korea or Iran. These so-called "B61 mod 12s" are meant to replace the 180 or so earlier models that are currently deployed in Western Europe. And those weapons are meant to assure our allies that if Russia is ever in the mood to invade, America will be there with a capital-B Bomb. "Continued funding support is essential to the long-term safety, security, and effectiveness of our nation's nuclear deterrent force," Gen. Robert Kehler, the head of U.S. Strategic Command, told Congress last year.

The B61 was first fielded in 1968. Unless critical components of the weapons are replaced – especially the radioactive tritium gas that makes the nuclear blast more efficient – the B61s might have to be withdrawn from the Continent by the end of the decade. "Old parts mean less-safe nukes. 60 years without an accidental detonation. We have a keen interest in keeping that record going," says John Noonan, a former U.S. Air Force nuclear missile officer and a spokesman for the House Armed Services Committee.

The logo for the B61 nuclear weapon upgrade. Photo: LANL The logo for the B61 nuclear weapon upgrade. Photo: LANL

A 2008 Secretary of Defense task force report (.pdf) cautions against underestimating the "political value our friends and allies place on these weapons, the political costs of withdrawal, and the psychological impact of their visible presence." But the same report notes that U.S. European Command – the Pentagon's top generals in the region – "believ[e] there is no military downside to the unilateral withdrawal of nuclear weapons from Europe." After all, America has thousands of additional warheads that could be delivered by intercontinental ballistic missiles, long-range bombers, and submarines.

All of which would make the push for the mod 12 upgrades tough to fathom under almost any conditions. But it's particularly odd now, when the Pentagon is under more fiscal pressure than it's felt since the 1990s. Just Tuesday, for example, the Chief of Staff of the Army announced plans to pare back the ground force's spending by likely cutting the number of troops to their lowest levels since before World War II. On January 3, 2013, the Defense Department will automatically lose another 9.4 percent of its budget – more than $500 billion over 10 years – unless Congress reverses the automatic, across-the-board cuts it previously put in place.

In other words: every billion counts. But while the rest of the Defense Department is looking to save money, the costs for the mod 12 program keep going up. In May, the project – which entails upgrading an estimated 400 weapons – had a price tag of $6 billion. By July, that number had grown to $10 billion. That's not only the equivalent of two-thirds of what the federal government plans to spend on all nuclear weapon enhancements over the next twenty years. "It would be less expensive to build solid-gold replicas of each of the 700-pound B61s, even at near-record gold prices," as Lewis recently noted in Foreign Policy.

One reason why: the mod 12 project — even though it's billed as a "life extension program" — isn't just about replacing the components of the weapons that are decaying or corroding. (Independent experts say that would take a mere billion or two.) When you swap out the B61's parachute for satellite-guided tail fin assembly, it introduces a new complication, Lewis adds. "An atomic bomb dropped without a parachute will explode before the airplane is safely away. That means [the federal government] must also redesign much of the packaging and components to survive 'laydown' – i.e., thudding into the ground and then exploding a few moments later." An internal Pentagon audit showed 15 of the 29 planned changes for mod 12 are still technologically immature.

But if the improvements aren't made soon, advocates say, they'll only get more expensive. "Modernization is expensive because we keep delaying it. Now we're at a point where, instead of making pragmatic annual investments in lab, stockpile, and delivery modernization – we have to do it all at once," says Noonan, the former missileer.

Pretty soon, there will be a choice: upgrade these nuclear weapons, or put them out to pasture. What would you do, if you were a cash-strapped Pentagon chief?