This winter we have learned there are no safe rooms.

For generations, Americans have lived with the conviction that wars were fought elsewhere, that civilian casualties happened to foreigners, that geopolitical tensions were for us to think about in our wood-paneled seminar rooms, not in our carpeted family rooms. Blessed with friendly neighbors and big oceans, we were powerful — and part of our power came from the knowledge that we were safe.

We don’t feel that way anymore. On Capitol Hill, the words “struggle” and “battle” were used as metaphors: the struggle for the Equal Rights Amendment, the battle for tax relief. The word “campaign,” which was military in origin, was employed to describe the way we chose our leaders. The phrase “holy war” was appended to “fights” — those pugilistic words sure are hard to avoid in politics — involving religious conservatives.

Here’s how much things have changed: Last week a Humvee mounted with an Avenger anti-aircraft missile system was deployed near the Capitol. But that was not all. Even people not given to paranoia avoided the subway system. The danger of biological contamination seemed real enough. Regular folks put gas masks in the spare bedroom. The threat of airborne contaminants seemed imminent. Hard-boiled commuters pored over maps to find plausible escape routes from crowded cities. The prospect of dying in a traffic jam at a bridge or tunnel seemed too much to bear.

It’s hard to resist the notion that we have already been hit by a terrorist attack this year. That attack was an onslaught of fear. And this time there is no Franklin Roosevelt saying that there is nothing to fear but fear itself. This time there is something to fear.

During World War II, America’s opponents didn’t specifically target civilians. But there were things to fear in the FDR years, of course, and the difference between that period and this is instructive. In 1941 and 1942, there was serious reason to worry about the survival of the nation itself. We know now that the vast mobilization of the arsenal of democracy made the difference in World War II, and that the factories and fighting forces of the United States combined to wear down the original axis of evil.

But it was not nearly that clear at the time. The oceanside bunkers on the Nahant shore near where I grew up in New England stand as reminders of the peril the United States faced, and felt, in that era.

There was, with Japan extending its reach across the Pacific and with Hitler moving effortlessly across Europe, legitimate basis to think that Great Britain and the United States might not be able to hold off their foes and that the nation might fall, that imperial Japan or Nazi Germany might be in power in Washington. In the end, victory was ours, but it was not inevitable. We see the logic in allied victory today, but it was not so clear then.

This is a different situation entirely. For all the uncertainties of the modern era, there is no chance that Osama bin Laden will ever rule the United States, no possibility that al-Qaida might take over the nation. But that does not mean the country does not face a serious threat today.

The threat today is not to American sovereignty, but to American values. And the principal American value is freedom.

In this peculiar war, freedom is under assault on two fronts. The first is obvious: Americans’ freedom to go about their daily, sometimes ordinary, lives is under attack as it has never been, not even in 1861, the last time the American front lines and the home front were indistinguishable.

Today, there are Americans afraid to take public transportation, gather in urban centers, visit their national monuments and memorials. (No one forgets, for example, that one of the most devastating suicide bombings ever occurred at a pizzeria in Israel. With the threat of suicide bombings here, every Pizza Hut is suddenly a potential venue for hostilities.)

But the second threat to American freedom is equally dangerous. It comes not from a foreign nation, nor from a terrorist group, but from our own government. The Justice Department is using the fear generated by the Sept. 11 attacks to promulgate policies (and work for legislation) that undermine the basic civil liberties the government says are at stake in the war on terror.

There were crackdowns on civil liberties in the Civil War, World War I and World War II, but those precedents — most of which have been repudiated by Americans and discredited by history — are not ample justifications for current crackdowns. Aggressive government actions against Arab-Americans are depriving the administration of much of the cooperation that authorities might otherwise easily receive. The zeal to preserve our values is resulting not only in a threat to our values, which would be serious enough. It is also resulting in a threat to American efforts to discover evidence of terrorist plots at home.

These are terrible times. No amount of duct tape is sufficient to provide Americans with the safety they crave. But jeopardizing American freedom is no way to assure Americans freedoms either.

David Shribman is a columnist for the Pittsburgh Post-Gazette.