Let the scaremongering begin.

Every time the Pentagon budget is vulnerable to cuts, we hear about the huge risks that would ensue. Defense jobs would get cut, depressing the economy. American military technology would fall behind. Terrorists would get a free hand. China would sneak up on us.

[Obama vows to veto DoD budget protections.]

So with $55 billion due to be cut from the Pentagon's budget next year, defenders of the military-industrial complex are once again warning of doom descending on America.

But it's the Pentagon's own wasteful spending that's a much bigger threat. Pentagon procurement has become so convoluted and dominated by lobbyists that billion-dollar weapon systems are commissioned a decade or two before they're actually fielded. Costs always rise, whether the weapon is relevant or not. Weapons are rarely junked, even when threats change--as they clearly did after the 9-11 terrorist attacks. Instead, favored programs are merely reconfigured and assigned new capabilities, raising costs even more.

The F-35 Lightning II fighter jet, the Pentagon's biggest procurement program ever, is the poster child for the kind of wanton spending the nation can no longer afford. The F-35, built by Lockheed Martin, got its start in the early 1990s, with the concept for a stealthy jet that the Air Force, Navy and Marine Corps could all use, theoretically making it cheaper than a trio of different jets unique to each service.

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It hasn't worked out that way. The first official plan, in 2001, called for 2,866 jets costing a total of $233 billion, according to the Government Accountability Office. The latest plan cuts production to 2,457 jets, yet the cost has risen to $397 billion. The cost per aircraft has doubled, from $81 million to $162 million, and that's without accounting for 10 years of inflation.

Budget analyst Winslow Wheeler--who calls the F-35 "the jet that ate the Pentagon"--argues that the total life-cycle cost of the program, including funds to operate and support the jet, could total a stunning $1.5 trillion or higher, which is more than the annual GDP of Spain.

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The Pentagon obviously needs capable fighter jets, along with modern ships, helicopters, and ground vehicles, cutting-edge intelligence-gathering technology, highly trained troops, and a rigorous support-system for veterans. But the time has long passed when we could afford the best of everything, cost be damned. As Wheeler reports in Foreign Policy, the F-35 became an unaffordable boondoggle because defense officials, abetted by members of Congress, insisted that the plane do practically everything: fight other jets, drop bombs, fly supersonic, have enclosed bomb bays for stealth, and come in variants able to land on aircraft carriers, unimproved airfields in the bush and conventional runways. What, no corkscrew?

This is what happens when the Pentagon gets virtually unlimited sums to build the world's most amazing toys. The Russians and Chinese must be happy to let us go broke building Cold War-style monstrosities, while they bone up on cyberwar and become experts at economic espionage.

Pentagon defenders point out that spending on national security is fairly modest these days relative to the size of the economy. During the Vietnam War, for instance, national-security spending totaled about 9.4 percent of GDP, according to Anthony Cordesman of the Center for Strategic and International Studies. During the 1980s, it was around 6 percent. Today, it's just 4.3 percent, and that includes spending on the war in Afghanistan and the rump operation in Iraq.

But America wasn't addicted to borrowing back then. The federal debt was only 38 percent of GDP at the end of the 1960s and 56 percent at the end of the 1980s. This year, the national debt will eclipse more than 100 percent of GDP, and keep growing. To continue building weapons like the F-35, meant to protect us against potential future enemies such as the Chinese, we'd basically be borrowing from lenders such as . . . the Chinese.

Paying down the national debt is eventually going to require tax increases on most Americans, along with cuts in popular programs like Medicare and Social Security. Most credible plans for fixing the nation's finances say it's imperative to rein in or simply kill extravagant programs like the F-35. Meanwhile, the biggest victories in the war on terror come when intelligence agents infiltrate the bad guys, steal their secrets and identify the location of their leaders--while an expendable, unmanned drone delivers a missile. No F-35 needed.

Rick Newman is the author of Rebounders: How Winners Pivot From Setback To Success. Follow him on Twitter: @rickjnewman.