Defense officials are increasingly concerned about the threats posed by drone swarms, technologies which can be accessed by smaller militaries or militias but which can present significant threats to aircraft carriers and more sophisticated weapons.

Retired Navy Admiral James Stavridis and former Marine special operations officer Elliot Ackerman wrote in an essay for The Wall Street Journal that warfare in the coming years will increasingly revolve around inexpensive weapons systems. They cited recent examples of drone swarms destroying Russian tanks in Ukraine, seaborne mines around Taiwan, and the drones which killed three American service members in Jordan earlier this year.

“The future of warfare won’t be decided by weapons systems but by systems of weapons, and those systems will cost less,” they wrote. “What doesn’t yet exist are the AI-directed systems that will allow a nation to take unmanned warfare to scale. But they’re coming.”

Stavridis and Ackerman compared the advent of the drone swarms to other historical examples of simple and cheap weapons overcoming more threatening technologies from superpowers. They referenced the phalanxes under Alexander the Great which used newly invented sixteen-foot spears to destroy Persian armored chariots and Indian war elephants.

The authors noted that multibillion-dollar American warships, such as the ones deployed to the eastern Mediterranean Sea last year as the war between Israel and Hamas started, could be vulnerable to relatively simple drones like the ones which killed service members in Jordan.

“A few Shahed drones are mostly a hassle, easily swatted from the sky except in the rare case when they score a lucky hit. They are best at blinding radars, disrupting communications, and attacking small numbers of troops,” they said. “But dozens or hundreds of drones in AI-directed swarms will have the capacity to overwhelm defenses and destroy even advanced platforms. Nations that depend on large, expensive systems like aircraft carriers, stealth aircraft, or even battle tanks could find themselves vulnerable against an adversary who deploys a variety of low-cost, easily dispersed and long-range unmanned weapons.”

One analysis from the Georgetown University Center for Security and Emerging Technology published four years ago indeed said that at least five Defense Department contracts, as well as two contracts from the People’s Liberation Army in China, have explicitly mentioned swarming.