The phrase "Home Front" was a metaphor that gained currency during World War I, with the intention of motivating a civilian population involved in total war. The image served to increase economic output and the purchase of war bonds, promote conservation and recycling of resources, and reconcile the citizenry to privation and rationing.

But in America's wars of today and in the future, "Home Front" is no longer a metaphor. Our enemies have no hope of defeating our armies in the field, and therefore explore asymmetrical methods to attack us. And though there are many facets to asymmetrical warfare -- as we saw in the pre-9/11 assaults on our interests in the Middle East and East Africa -- the Holy Grail of such a strategy is attacking the American homeland. As long as this is true, blocking the enemy's ability to carry out such attacks is essential to successfully prosecuting our wars.

To this end, as of October 1 all men ages 16 to 45 from Saudi Arabia, Pakistan and Yemen visiting the United States are fingerprinted, photographed, and questioned upon their arrival. They also have to report to the INS periodically during their stay, and their departure must be recorded.

Visitors from Iran, Iraq, Syria, Sudan, and Libya are already required to undergo such registration, and potential visitors from Egypt and Jordan have been advised that they might have registered as well.

These measures aim to fix the enormous problems in our immigration system that became impossible to ignore after the September 11 attacks. A Center for Immigration Studies analysis of the immigration histories of 48 foreign-born Al-Qaeda operatives who committed crimes in the United States over the last decade (The report can be accessed at: http://www.cis.org/articles/2002/terrorpr.html ) found that nearly every element of the immigration system has been penetrated by the enemy. Of the 48 (including the hijackers), one-third were here on various temporary visas, another third were legal residents or naturalized citizens, one-fourth were illegal aliens, and the remainder had pending asylum applications. Nearly half of the total had, at some point or another, violated immigration laws.

The government's response to this penetration of our immigration system certainly appears muscular. Last year's USA Patriot Act contained immigration-related provisions that, among other things, finally gave the INS and State Department access to the FBI's criminal databases. The border security bill signed by the President in May includes a mandate for the creation of a visa card containing a fingerprint or other identifier to be used by "nonimmigrant" foreigners (tourists, students, businessmen, etc.) -- so that the INS would actually know whether a visitor actually leaves when his time expires, something we presently cannot determine.

The agencies responsible for immigration have also made changes. The INS, for instance, decided that it should start looking for the 300,000-plus foreigners who have absconded after being ordered deported, and these names are being entered into the FBI's national crime database (though only about 900 or so have so far been located). The State Department, meanwhile, has intensified scrutiny of visa applications from Muslim countries.

But as frenetic as this activity seems, the White House and Congress are clearly uncomfortable with the essential security function of immigration control. For instance, the State Department continued operating, and loudly defending, an express visa program in Saudi Arabia run by private travel agents, even after it was discovered that three of the hijackers had benefited from it. It was discontinued only after a congressional uproar.

Likewise, INS Commissioner James Ziglar, a libertarian former business executive, is still at the helm of that troubled agency (though he has announced his retirement by the end of this year). Ziglar's unsuitability for a security role was made clear after the attacks, when he repeatedly observed that "We're not talking about immigration, we're talking about evil." Elsewhere he even employed the "then the terrorists will win" cliché, saying, "If, in response to the events of September 11, we engage in excess and shut out what has made America great, then we will have given the terrorists a far greater victory than they could have hoped to achieve" -- as though delaying the arrival of foreign visitors was equivalent to mass-casualty suicide attacks.

Furthermore, the border security bill mentioned above is quite modest in scope. Hailed as a great advance, the law in fact merely lifted some of the more ridiculous limitations on the INS's ability to do its job and mandated reforms that won't bear fruit for years, if ever. And even the revival of long-ignored immigration-control tools, such as alien registration and change-of-address requirements, often come at the expense of efforts that would deliver more bang for the buck -- but which are politically problematic. One such measure would be to roll out the experimental system already developed by the INS that allows employers to verify a new hire's work eligibility. Though less comprehensive than attempting to track all changes of address, such a system would give the INS much more reliable information as to the daytime whereabouts of the large majority of aliens. Of course, it would also significantly limit illegal immigration, and thus is unacceptable to interest groups that benefit from the status quo.

Because of this ambivalence about immigration controls, we remain vulnerable to attack. The vast majority of visa applicants are still never interviewed by U.S. consular officers; there is no significant enforcement of immigration laws within the country; efforts to use the military in a support role to supplement the Border Patrol have been rebuffed; and worst of all, government at all levels is blurring the distinction between legal and illegal residents by providing illegal aliens with driver's licenses, offering them in-state college tuition discounts, and encouraging financial institutions to open bank accounts for them using identifications issued by foreign governments.

This lack of seriousness about the security imperative of immigration control is particularly troubling because it applies not only in this war but also in any future war the United States is likely to fight. In a sense, immigration control is to asymmetrical warfare what missile defense is to strategic warfare. There are other weapons we must use against an enemy employing asymmetrical means - more effective international coordination, improved intelligence gathering and distribution, special military operations -- but in the end, ineffective immigration control leaves us naked in the face of the enemy.

Thus, even if Al-Qaeda is dismantled and the threat of radical Islam recedes, immigration controls will remain vital to the security of the United States. As long as our military power is overwhelmingly superior to all other nations, future enemies will inevitably employ asymmetrical means to attack us. Saddam, for instance, is obviously no Islamist, but his best prospect for striking at us, especially for revenge attacks if his cause is already lost, is through domestic terrorism. Likewise, the extensive exploration of asymmetrical tactics among Chinese military planners includes discussion of the use of immigrants as fifth columnists.

America's border is not an obstacle to be overcome by travelers and businesses, but instead is a critical tool for protecting America's national interests. Thus there is probably no more important defensive weapon in our arsenal than a well-functioning immigration system. We neglect it at our peril.

Mark Krikorian is the Executive Director of the Center for Immigration Studies (http://www.cis.org).