On June 1, Ukraine’s security services launched a covert strike on five air bases across Russia. More than 100 attack drones smuggled into Russia in plywood cabins on trucks driven by unsuspecting Russians destroyed bombers sitting on tarmacs as far away as the Belaya air base in Siberia, around 3,000 miles from Kyiv. According to Ukrainian government sources, the strikes took out about one-third of Russia’s long-range bomber force and cost Moscow roughly $7 billion. Dubbed Operation Spiderweb, it was one of the most spectacular and daring attacks to date of the war in Ukraine. It was also a dramatic warning of a growing threat to American soil.

In an essay in Foreign Affairs in January 2022, one of us (Donilon) warned of this threat. Back then, America’s vulnerability to this possibility seemed to be a “failure of imagination,” echoing the 9/11 Commission’s famous conclusion about the United States’ failure to anticipate the 2001 attacks on the World Trade Center. Today, the drone threat is no longer difficult to imagine. States can use them to sow economic disruption or to spy on sensitive sites, lone-wolf actors can use them for political violence, and hobbyists can accidentally crash them into critical infrastructure.

Both the Biden and Trump administrations have taken steps to protect the country from drones, such as specifying federal roles and responsibilities, banning drone flights over certain sensitive sites and special events, and investing in counterdrone technology and its deployment. Recent legislation goes even further to close jurisdictional gaps. But despite this progress, the United States has not kept pace with the threats. Vulnerabilities remain, including inadequate systems for identifying and restricting drones in U.S. airspace, limited funding for advanced counterdrone systems capable of protecting sensitive infrastructure and mass gatherings of people, and supply chain risks tied to China’s dominance of the global drone market.

The United States, in other words, still lacks a comprehensive drone defense. The good news is that the country and its partners have the means and ability to mitigate the domestic threat from drones, and there is bipartisan consensus in Washington for doing so. They just need the bureaucratic and political will to act before a crisis forces them to.

The risk from drones has evolved dramatically since 2022. Russia’s war against Ukraine has demonstrated the lethality of drones, which according to Ukrainian government estimates are now responsible for 70 percent of all casualties. The war in Ukraine has also served as a testing ground and innovation accelerant for unmanned aircraft systems (UAS), including the mass production of first-person-view drones, the development of fiber-optic drones that can travel for miles and cannot be thwarted by radio frequencies, and long-range strike drones that are ever more capable of effectively hitting targets such as energy and civilian infrastructure. Skilled drone pilots can guide their payloads into the open hatch of a tank and have been recording such attacks to score propaganda points for Kyiv or Moscow. Ukraine is manufacturing some four million drones a year—by some estimates more than all NATO countries combined—while Russia is making around two million per year. Mounting a defense, meanwhile, has been difficult, with neither Russia nor Ukraine able to find scalable and broad countermeasures to protect itself against the onslaught.

During this time, drones have become ever more present in U.S. skies as well. According to the Federal Aviation Administration, more than 800,000 drone operators are registered in the United States. But the number of actual drones is far higher because of the many hobbyists operating small drones that fall below registration thresholds and because operators can use a single registration to fly multiple drones.Drones are now being used for everything from monitoring crop health to assisting firefighters and law enforcement. And the day when drones........

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