Few things shock anymore, but it came as a bit of a surprise last week when Rep. Paul Ryan, chairman of the House Budget Committee, revealed how little he knows about the making of the budget.

The moment occurred on March 29, when Ryan told a National Journal forum in Washington, “We don’t believe the generals are giving us their true budget.”

Ryan backpedaled after Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, said that he and the other chiefs didn’t appreciate being called liars. “I really misspoke,” Ryan said on CNN—invoking the word often used by politicians who say what they mean, then realize they’ve sounded foolish. He added, “I was clumsy in how I was describing the point I was trying to make.”

He went on, “What I was attempting to say is, President Obama put out his budget number for the Pentagon first … and then they began the strategy review to conform the budget to meet that number. We think it should have been the other way around.”

That was an odd thing for him to say. Ryan is the author of the Republicans’ alternative budget plan, a much-bandied contender for the No. 2 slot on Mitt Romney’s presidential ticket, and, according to David Brooks, “the most intellectually formidable member of the House.” Surely he knows that the process he finds so objectionable—the president comes up with a budget, the generals fit their plans around it—is the way things have always worked, and for good reasons.

The first reason is obvious: The American military answers to civilian control. This principle has been hammered into officers, at every step of their training, for at least the past 60 years when Gen. MacArthur challenged President Truman and went up in flames. Almost every general since has accepted, even welcomed, the arrangement.

The second is a bit subtler but still basic: This is the nature of a budget, not just for the Pentagon, but for every government agency, every company, every household. A budget is a tool for managing resources. Everyone wants more money, but the pot is finite; a budget resolves the tension.

Ryan should know this. The House committee he chairs was created in 1974 precisely to lay down an annual budget resolution—setting priorities on how to divvy up the federal budget (x dollars for defense, y for education, z for welfare, etc.) and thus imposing limits on how much the other, more parochial committees could dole out to the agencies they oversaw (or, more often, indulged). Things didn’t work out quite that way—the planners underestimated the power of the other panels’ chairmen and their clients—but the idea was to create a sort of supercommittee that could view the roles and missions of each federal department in the broader context of the nation’s resources and needs.

Certainly, the generals and admirals would like to have a larger budget; they’d like to have more troops, guns, missiles, planes, ships, and all the rest. The heads of all the other government agencies would like to have more of whatever they’re accustomed to buying, too.

By not giving these public servants everything they request, the president (or Congress) might be incurring real costs. Cutting budgets may mean more hungry children, less drinkable water, more perilous roads, or—yes—a less capable military.

Budgets manage something else besides resources: They manage risk. One could make the case (and Paul Ryan’s budget sets out to make it) that far fewer risks should be taken with the military’s budget. An unrepaired road might result in the deaths of a few people, but a weak defense could wreck the nation.

The argument is unassailable, but, that said, the burden falls on lawmakers like Ryan to ensure that the Pentagon’s programs are actually vital to the national defense—or at least that the risks of cutting a certain program are too great to incur.

This is precisely what Ryan has failed to do—though, in fairness, none of his colleagues, in either party, have done much better. They haven’t subjected the defense budget to a systematic analysis of what is necessary and what isn’t; they haven’t even sought to scope out what “necessary” means.

All through the first decade of this century, the Pentagon’s managers failed to do this as well. In the wake of 9/11, they got whatever they wanted, and anyone who resisted was labeled “soft on terrorism,” whether or not the programs they resisted had anything to do with the “war on terror.” What discipline they once had (and it was never stern) went slack amid the free-for-all.

With the appointment of Robert Gates as secretary of defense in 2006, the long knives came out of the drawer, to some extent anyway.

Take, for instance, Gates’ decision to halt production of the F-22 Raptor at 183 planes instead of proceeding to buy all 387 that the Air Force wanted. One reason he did this was that, according to the Air Force’s own analysis, 387 of the planes would be needed only if the United States were to fight two simultaneous wars against foes of comparable strength (e.g., a revived Russia and an emergent China). Gates made an explicit calculation that this scenario was extremely unlikely and that, therefore, halting the F-22 was a move of very low risk.

It was a risk, though, and he said as much. Every decision carries some risks. One job of a leader is to weigh them.

Gen. Dempsey and the other chiefs who took offense at Ryan’s remark have actually been doing a lot of risk-weighing, as chiefs are often forced to do when wars end and the budget axe begins to chop.

When they testify to Congress, military officers present the case for the budget they’ve submitted. But they also express an appraisal—their “best professional judgment”—of its consequences. They will say that cutting a weapons program, or buying fewer of them than they’d initially advocated, has “low risk” or “medium risk” or “high risk.” Their assessments are worth noting, though even then not following blindly.

The fact is, the Pentagon’s program managers are still a bit woozy with Bush-era extravagance. Dempsey and his colleagues are slapping their faces, warming the coffee, rolling up their sleeves … (insert your favorite clichéd metaphor).

Still, it’s worth noting that in 1985, at the height of President Ronald Reagan’s Cold War arms build-up, the Pentagon’s budget (adjusted for inflation, to make it comparable to today’s dollars), amounted to $575 billion.

By comparison, President Obama’s defense budget for next year totals $525 billion, not including the cost of the wars in Afghanistan and elsewhere. When the wars are included (and Reagan’s budget included the cost of a few “small wars”), it amounts to $671 billion.

In other words, despite Ryan’s criticism of the administration’s cuts, Obama is requesting (again, in inflation-adjusted terms) either 7 percent less or 16 percent more than Reagan at his peak. (By the way, personnel costs don’t explain the growth. Personnel accounts for about one-third of the defense budget, now and in the Reagan era. Pay and benefits are much higher now, but the number of active-duty troops is much lower, so the two trends cancel each other out.)

I’ve said this before, but it bears repeating: In an era when we face no foes of remotely comparable military power, how could it be that we need to spend roughly as much money as we spent when the Soviet Union was still alive, the Cold War was heating up, the border between East and West Germany was an armed garrison, and the nuclear arms race was spiraling upward?

Yes, we face foes today, but they don’t confront us with echelons of tanks, armadas of fighter-bombers, or giant aircraft carriers fronting vast blue-water navies—nor do the threats they pose require the deployment of such big-ticket items to the extent that they once did.

If Congressman Ryan wants to do his job, follow through on the logic of his critique, and start analyzing the defense budget, that would be a service. Otherwise, he’s just jabbering.