Last Friday, tragedy struck Oslo, Norway, as homegrown terrorist Anders Behring Breivik detonated a car bomb in the heart of the city and then traveled to a nearby island and opened fire on a youth camp. In a mere 90 minutes, one gunman took the lives of 76 people, many of them only teenagers. Details of the attack and the response continue to unfold. This incident is a stark reminder that armed assaults have become the new Improvised Explosive Device (also used in the Oslo attacks), the latest innovation in spreading terror. There is no excuse not to prepare now for this kind of threat.

The attacks in Oslo are not the first time the world—or the United States for that matter—has seen an armed terrorist assault, nor is it likely to be the last. Armed assaults incorporate a range of tactics traditionally associated with terrorist activity, including suicide and car bombings, kidnapping, sabotage, and assassination, and are a significant and viable threat to the United States. “Active shooter” incidents, such as those in Mumbai, Fort Hood, and, most recently, in Oslo, are of significant concern. The Department of Homeland Security describes an active shooter as “an individual actively engaged in killing or attempting to kill people in a confined and populated area; in most cases, active shooters use firearms and there is no pattern or method to their selection of victims. Active shooter situations are unpredictable and evolve quickly.”

While such “small-scale” incidents are not likely to bring down the country, they can produce significant physical and psychological damage with little technical skill and at a fairly modest cost. No longer is it necessary for would-be terrorists to attend a terror training camp in the flesh. Instead, anyone with a computer and Internet access can connect to the vast array of terrorist materials online, including extensive explosives and weapons training.

In the United States, this threat is certainly nothing new. In the decade since 9/11, there have been at least 40 thwarted terrorist attacks against the United States. Of these 40 thwarted attacks, at least 13 involved planned assault-style tactics. In 2007, for example, six men were arrested in a plot to use assault rifles and grenades to attack and kill U.S. soldiers at the Fort Dix Army post in New Jersey, and in 2011 Ahmed Ferhani and Mohamed Mamdouh were arrested by the New York Police Department after attempting to purchase a hand grenade, guns, and ammunition to attack an undetermined Manhattan synagogue. Additionally, of the terror plots since 9/11 that were not foiled—the Little Rock military center shooting, Los Angeles airport ticket counter shooting, and Fort Hood shooting—all three involved armed assault-style attacks.

While public concern has often centered on the threat of large-scale attacks like those that occurred on 9/11, smaller-scale attacks by individuals like that in Oslo also present a significant threat that cannot be ignored. The best defense is, of course, to unearth and thwart these attacks before they reach the execution stage. If they do occur, however, the law enforcement and emergency management response must be swift, integrated, and well organized. Washington can help. Congress and the Administration should seek to:

Enhance response capabilities. Terrorist tactics are continually evolving; thus, the United States must be prepared for the wide array of potential terrorist tactics. Presently, the Department of Homeland Security maintains 15 disaster planning scenarios used by federal, state, and local officials in disaster preparedness and response exercises. These National Disaster Scenarios should be revised to include armed assaults.

Preserve essential counterterrorism tools like the PATRIOT Act. The best way to deal with the threat of armed assaults on the United States is to prevent the attacks before they occur. This requires effective counterterrorism tools and methods of intelligence gathering to help investigators track down leads and stop threats before they materialize. Enacted shortly after 9/11, the PATRIOT Act modernizes intelligence and legal authorities and ensures that terrorism investigators have the same tools as those available in criminal investigations. The PATRIOT Act, a demonstrated counterterrorism tool, has proved vital in thwarting several of the 40 terrorist attacks that have been prevented since 9/11. Congress should resist efforts to erode the act’s provisions and ensure its permanent authorization.

Strengthen homeland security information sharing and partnerships. State and local governments are key partners in protecting the homeland. Local law enforcement, for instance, knows its communities and is more likely to detect when something is not right. To ensure that state and local governments are equal partners in the homeland security enterprise and that all players have the information needed to protect the nation, information must flow in both directions. Likewise, the U.S. must work to enhance its partnerships and communication with key allies. Several of the terrorist plots foiled since 9/11 have been thwarted through information sharing with key international partners. These vital relationships must not be overlooked.

Protecting the nation against potential attacks requires the capabilities to halt attacks before they occur. It is unrealistic to expect that the United States can thwart every attack every time; however, an “all-hazards” approach to security and effective counterterrorism, intelligence, and information-sharing programs offer the best defense.

James Jay Carafano, Ph.D., is Deputy Director of the Kathryn and Shelby Cullom Davis Institute for International Studies and Director of the Douglas and Sarah Allison Center for Foreign Policy Studies, a division of the Davis Institute, at The Heritage Foundation.