NATO is being pushed to the breaking point by a most surprising foe. It isn't Russian troops, Iranian nukes or a ragtag collection of Afghan tribes that threaten to overwhelm the most powerful military alliance in history, but rather a lack of will – and the eagerness of virtually every NATO member to balance their budgets by slashing their militaries. Next month's NATO summit in Chicago offers alliance leaders an opportunity to either ensure NATO's future, or shove it toward its Waterloo.

Fellow NATO nations generally follow Washington's lead, which is cause for deep concern given that Washington is engaged in massive defense cuts:

• The Pentagon has proposed cuts of $487 billion over the next decade. There are plans to cut the number of deployed carriers to 10. Marine Corps end strength will be cut from 202,000 to 182,000. The Army will be slashed from 570,000 troops to 490,000. Seven Air Force squadrons are on the chopping block.
• Pentagon plans call for real dollar-figure cuts in spending on the F-35,  Predator and Reaper UAVs, UH-60 Blackhawks, F/A-18 Super Hornets, M1 Abrams upgrades, Stryker armored vehicles, ground- and sea-based missile defenses, next-generation aircraft carriers, Virginia-class submarines, and a number of space-based assets.
• The Obama administration is even floating huge cuts in the U.S. nuclear deterrent, which serves as a protective umbrella for the United States and its allies. The most reckless proposal would slash the deterrent from 1,550 warheads to 300.

The rest of NATO is following suit:

• Britain is cutting troop strength by 10 percent, retiring 40 percent of its tanks and cutting its fleet of destroyers and frigates from 23 ships to 10.
• France is slicing 4 percent from its defense budget.
• Italy is cutting defense spending by 28 percent, troop strength from 183,000 to 150,000 and F-35 purchases from 131 to 90.
• Germany will reduce civilian and military numbers by 90,000, slash the Tornado bomber fleet from 185 to 85 and retire eight frigates.
• The Netherlands is cutting 12,000 military and civilian defense posts.

These cuts might make sense if peace were breaking out all around the world. But we know that the very opposite is true.

NATO is still at war in Afghanistan (at least, some of NATO). Iran is racing ahead with its nuclear-weapons program. North Korea is less stable and more paranoid than ever. Terrorist networks like al-Qaida still have the ability to strike targets in the United States and Europe; indeed, the group is gaining ground in Yemen. Nuclear-armed Pakistan is under assault from within, as is oil supplier Nigeria. The Arab Spring revolution has triggered a civil war in Syria; what happens if, or when, the revolution spreads to oil-rich Saudi Arabia or Kuwait? And what path will the new governments in Egypt and Libya choose?

Then there are the big worries. While NATO declaws itself, China is boosting military spending by 11 percent this year, capping double-digit increases in nine of the past 10 years. That unparalleled buildup has empowered Beijing to bully its neighbors, launch cyberattacks, conduct provocative military operations in space, and deploy huge arsenals of missiles, submarines and warplanes to project its power and limit Washington's. Likewise, Russia – in the midst of a 65-percent increase in military spending over five years – is making claims in the Arctic, occupying parts of Georgia, blocking international action in Iran and Syria, and deploying nuclear missiles to areas bordering NATO states.

It's no wonder that Norwegian Defense Minister Espen Barth Eide worries about NATO's ability "to deliver if something happens in the trans-Atlantic theater of a more classical type of aggression." Think Iranian missile salvos, a Russian lunge at Estonia, an EMP blast or a 9/11-style siege.

Speaking of 9/11, then-Defense Secretary Robert Gates noted last summer that total European defense spending fell by 15 percent in the decade after 9/11, meaning that Europe's deficit of will predates the Great Recession. Most NATO nations essentially stopped investing in defense after the Cold War and instead relied on the United States to carry the burden. In fact, the United States now accounts for 75 percent of NATO's defense spending – far above the U.S. share of 50 percent during the Cold War – and just five NATO members meet the alliance's standard of investing 2 percent of GDP on defense.

The consequences are on full display in Afghanistan, where the United States is contributing 71 percent of all forces; where non-NATO members Australia, Georgia and Sweden have more troops deployed than several founding members of the alliance; and where NATO has been exposed as a "one for all" public good rather than an "all for one" alliance.

In Libya, without the United States in the lead, NATO was found woefully lacking in munitions, targeting and jamming capabilities, midair refueling planes, reconnaissance platforms, drones, and command-and-control assets – just about everything needed to conduct a 21st-century air war. After Libya, NATO Secretary General Anders Fogh Rasmussen called on the alliance to "aim at narrowing the economic and technological gap between the United States and Europe." That seems unlikely given the massive military retrenchment now under way. Equally unlikely is NATO engaging in another Libya-style policing mission any time soon, let alone another open-ended, Afghanistan-style nation-building campaign.

A year ago, Gates openly worried about NATO's "lack of will" and "lack of resources." In a very real sense, the United States has supplied both, especially in recent years. As America's will (see Libya and Afghanistan) tapers and its resources (see the 2013 defense budget) shrink, it stands to reason that NATO's global reach and role will follow a similar trajectory.

Where that trajectory ultimately leads the alliance – back to focusing on deterrence or into irrelevance – remains to be seen.