You do not respond to international terrorism by convening grand juries and issuing subpoenas. You declare war.

Not a "police action." Not a "resolution authorizing the use of force." War.

The President should ask for -- and Congress should approve -- a formal declaration of war to address terrorism. Not just the attacks of Sept. 11, but the ability of terrorists and their state benefactors to conduct further attacks.

It may sound quaint to our modern ears. After all, the so-called "law of war," based on conventional relations between nation-states, assumes that one nation has attacked another. It defines war as "that state in which a nation prosecutes its right by force."

But concepts of war and warfare never have been static. Over the past 20 years, we've seen something new: organized, non-state actors conducting war, sometimes acting as proxies, sometimes for their own purposes.

We have defined this new warfare as "terrorism" and attempted to solve it as though it were a law-enforcement issue. We have tried to deal with these situations largely by "outlawing" through the criminal process hijackings, hostage-taking and other such activities.

But the events of Sept. 11 require that we -- and the community of civilized nations -- change our notions of "war."

Our enemies haven't shown a lack of resolve because of the legal process. On Sept. 11, their warriors weren't worried about violating anti-hijacking statutes or facing murder convictions. Their own convictions required them to ignore our notions of criminal deterrence.

The people who planned and carried out these attacks don't see themselves as "criminals." They see themselves as warriors against the United States, and it would be irresponsible for us not to treat them as such.

The concepts articulated by Karl von Clausewitz, the 19^th Century Prussian strategist who influenced so much of the West's thinking on warfare, are equally relevant today. War, he said, "is the continuation of politics by other means … war is thus an act of force to compel our enemy to do our will."

If the death and destruction we see around us are the same as in war -- and it's impossible to look at the tally from the attacks on New York and Washington and think otherwise -- then we must respond as in war. And the only appropriate response is a military one -- under the laws of war, not under the U.S. criminal code.

When President Reagan responded to Libya's involvement in a terrorist attack that killed one American serviceman with a military mission, he sent a clear message that the only way to deal with terrorism is with force. The bombing of Libyan targets -- including Libyan leader Muammar Qadhafi's bunker -- combined with restrictions on commercial engagement with that country caused that regime to think twice about terrorism. It minimized Libya's sponsorship of terrorism.

We should heed this lesson about the need for a military response. But the problem cannot be limited to a one-time action.

This declaration and the resulting policy should allow for the use of all necessary means, including the use of military force, to destroy the organization(s) responsible for these attacks, along with other organizations that may have aided or abetted these attacks, and to remove from power any foreign government that likewise aided and abetted these attacks.

The fact that we have not yet officially identified our combatants is not an obstacle. President Thomas Jefferson declared war on the Barbary pirates who were robbing and looting American ships in the early 1800s without having a specific nation named as our enemy.

Along with a declaration of war, President Bush needs to press Congress to approve every dime of his requested $18 billion in additional military spending for 2002. This is not a war budget, however; it's a down payment on stopping the decline of our peacetime military.

Even more money will be needed to wage a successful war. Now's not the time for Congress to pinch military dollars -- or pretend that the nature of war hasn't changed.

In its opinion and judgment on the crimes of the Nazi regime, the International Military Tribunal (Nuremberg Tribunal) noted in 1946 that the law of war "is not static, but by continual adaptation follows the needs of a changing world."

The world changed on Sept. 11 and our response should be a sustained, aggressive response to international terrorism, its organizers, proponents, financiers and supporters. The thousands of Americans who were killed deserve nothing less.

Edwin J. Feulner, Ph.D. is president of The Heritage Foundation, a Washington-based public policy research institute.