THE relative calm that America’s armed forces have imposed on Iraq is certainly grounds for cautious optimism. But it also raises some obvious questions: how was it achieved and what does it mean for future defense planning?

Many analysts understandably attribute the success to our troops’ following the dictums of the Army’s lauded new counterinsurgency manual. While the manual is a vast improvement over its predecessors, it would be a huge mistake to take it as proof — as some in the press, academia and independent policy organizations have — that victory over insurgents is achievable by anything other than traditional military force.

Unfortunately, starry-eyed enthusiasts have misread the manual to say that defeating an insurgency is all about winning hearts and minds with teams of anthropologists, propagandists and civil-affairs officers armed with democracy-in-a-box kits and volleyball nets. They dismiss as passé killing or capturing insurgents.

Actually, the reality is quite different. The lesson of Iraq is that old-fashioned force works. Add 30,000 of the world’s finest infantry to the 135,000 battle-hardened troops already there, as we have done, and the outnumbered insurgency is in serious trouble. Detain thousands more Iraqis as security threats, and the potential for violence inevitably declines. Press reports indicate that the number of Iraqis in prison doubled over the last year, to 30,000 from 15,000; and while casualty figures are sketchy, military officials told USA Today last September that the number of insurgents killed was already 25 percent higher in 2007 than in all of 2006.

And while the new counterinsurgency doctrine has an anti-technology flavor that seems to discourage the use of air power especially, savvy ground-force commanders in Iraq got the right results last year by discounting those admonitions. Few Americans are likely to be aware that there was a fivefold increase in airstrikes during 2007 as compared with the previous year, which went hand in hand with the rest of the surge strategy. Going high-tech once again proved to be highly successful.

Regrettably, two other uncomfortable developments also helped suppress violence. First, the Iraqi population has largely segregated itself into sectarian fiefs. Second, supposedly “reformed” insurgents now dominate Anbar Province. While these Sunni partisans have for the moment sided with the United States, can we assume they’ve bought into the idea of a truly pluralistic and democratic Iraq?

Nonetheless, fans of the counterinsurgency manual are using it as a bludgeon against anyone who wants to plan to fight the next war rather than the last one. Their line of thinking holds that our next war will be a replay of Iraq, and thus most of our armed forces should be structured for counterinsurgency.

But this ignores other potential threats. Should we simply wish away China’s increasing muscle, or a resurgent Russia’s plans for a fifth-generation fighter that would surpass our top of the line jet, the F-22 stealth fighter? Moreover, does anyone really believe that creating corps of civil affairs officers will deter North Korea or Iran?

Yes, there is always the possibility that we may again find ourselves battling an insurgency, and the manual has many great ideas. Furthermore, the proposal for a 20,000-strong adviser corps to help Iraqi local forces fight insurgents ought to be green-lighted.

The problem emerges when we consider pouring excessive resources into preparing for only one kind of conflict. Doing so would put us at real risk of losing the technological superiority that has kept America’s vastly more dangerous threats at bay. Consider, for example, that our warplanes are on average more than 25 years old.

The enormous cost of the Iraq war, not to mention the loss of life on both sides, would seem to counsel against the idea of a similar operation elsewhere. Looking ahead, America needs a military centered not on occupying another country but on denying potential adversaries the ability to attack our interests. This is not a task for counterinsurgents, but rather for an unapologetically high-tech military that substitutes machines for the bodies of young Americans.

The unemployment report on Friday was brutally bad. Unemployment rose in December, while job creation was minimal — and it’s highly likely, for technical reasons, that the job number will be revised down, showing an actual decline in employment.

It’s the latest piece of bad news about an economy in which the employment situation has actually been deteriorating for the past year. It’s no longer possible to hope that the effects of the housing slump will remain “contained,” as one of 2007’s buzzwords had it. The levees have been breached, and the repercussions of the housing crisis are spreading across the economy as a whole.

It’s not certain, even now, that we’ll have a formal recession, although given the news on Friday you have to say that the odds are that we will. But what is clear is that 2008 will be a troubled year for the U.S. economy — and that as a result, the overall economic record of the Bush years will have been dreary at best: two and a half years of slumping employment, three and a half years of good but not great growth, and two more years of renewed economic distress.

The November election will take place against that background of economic distress, which ought to be good news for candidates running on a platform of change.

But the opponents of change, those who want to keep the Bush legacy intact, are not without resources. In fact, they’ve already made their standard pivot when things turn bad — the pivot from hype to fear. And in case you haven’t noticed, they’re very, very good at the fear thing.

You see, for 30 years American politics has been dominated by a political movement practicing Robin-Hood-in-reverse, giving unto those that hath while taking from those who don’t. And one secret of that long domination has been a remarkable flexibility in economic debate. The policies never change — but the arguments for these policies turn on a dime.

When the economy is doing reasonably well, the debate is dominated by hype — by the claim that America’s prosperity is truly wondrous, and that conservative economic policies deserve all the credit.

But when things turn down, there is a seamless transition from “It’s morning in America! Hurray for tax cuts!” to “The economy is slumping! Raising taxes would be a disaster!”

Thus, until just the other day Bush administration officials were in denial about the economy’s problems. They were still insisting that the economy was strong, and touting the “Bush boom” — the improvement in the job situation that took place between the summer of 2003 and the end of 2006 — as proof of the efficacy of tax cuts.

But now, without ever acknowledging that maybe things weren’t that great after all, President Bush is warning that given the economy’s problems, “the worst thing the Congress could do is raise taxes on the American people and on American businesses.”

And even more dire warnings are coming from some of the Republican presidential candidates. For example, John McCain’s campaign Web site cautions darkly that “Entrepreneurs should not be taxed into submission. John McCain will make the Bush income and investment tax cuts permanent, keeping income tax rates at their current level and fighting the Democrats’ plans for a crippling tax increase in 2011.”

What “crippling” tax increase, which would tax entrepreneurs into submission, is Mr. McCain talking about? The answer is, proposals by Democrats to let the Bush tax cuts for people making more than $250,000 a year expire, returning upper-income tax rates to the levels that prevailed in the Clinton years.

And we all remember how little entrepreneurship there was, how weakly the economy performed, during the Clinton years, right? Oh, wait. (I’ve put some charts comparing job performance during the Clinton and Bush years on my Times blog, krugman.blogs.nytimes.com. It’s pretty startling how comparatively weak the Bush era looks.)

Never mind. The whole point of scare tactics is that they can work even in the face of inconvenient facts.

And what I’m not sure about is whether the Democrats are ready for the fight they’re about to face.

Not to put too fine a point on it, Barack Obama won his impressive victory in Iowa with a sunny, upbeat message of change.

But there’s a powerful political faction in this country that understands very well that any real change will create losers as well as winners. In particular, any serious progressive reform of health care, let alone a broader attempt to reduce middle-class insecurity and inequality, will have to mean higher taxes on the affluent. And members of that faction will do whatever it takes to scare people into believing that change means disaster for the economy.

I don’t think they’ll succeed. But it would be a big mistake to assume that they won’t.