The Rise of the Drone Boats

It was the most expensive war game in US military history, and the outcome was a disaster.

Conducted in 2002 and costing roughly $250 million to plan over two years, the so-called Millennium Challenge exercise pitted a Blue team representing the United States against a Red team representing a fictional state in the Persian Gulf, usually understood as Iran or Iraq, as a means of testing the US Defense Department’s post-Cold War doctrine based on advanced new technologies and concepts.

Despite the Blue Team’s ostensible military and technological superiority, the Red team, led by Marine Corps Lieutenant General Paul Van Riper, unleashed complete chaos upon its adversary using unanticipated asymmetric and unconventional tactics—most notably, a complex cruise missile attack followed by a wave of explosive-laden kamikaze speedboats that, in one 10-minute swarm, sank 19 Blue team warships and inflicted 20,000 simulated casualties on his adversary. The exercise was so disastrous that the Pentagon went on to impose arbitrary constraints on the Red team that all but ensured a Blue team victory, prompting Van Riper to quit as team leader in protest.

As part of its complicated legacy, Millennium Challenge 2002 had undermined the very advanced technologies it sought to validate, proving that a handful of small watercraft could, when deployed in coordinated swarms amid a larger attack, successfully outmaneuver larger surface warships with potentially deadly consequences. It’s a lesson the Pentagon all but ignored by stacking the deck in favor of the Blue team following the Red team’s initial victory. Now, more than two decades later, its lessons are playing out in battlefields around the world.

View of an explosion on a ship that Houthis say is an attack by them on Greek-owned MV Tutor in the Red Sea, dated June 12, 2024, in this screen grab obtained from a video.Photograph: HOUTHI MEDIA CENTRE/Reuters

Unmanned surface vessels (USVs) loaded with explosives and other lethal payloads are proving a fearsome weapon for ostensibly outgunned fighting forces. Amid Russia’s ongoing invasion, the Ukrainian military has successfully driven Moscow’s Black Sea Fleet from its safe harbor in Sevastopol in the annexed Crimean peninsula using a growing fleet of weaponized drone boats that aren’t just successfully targeting other surface vessels, but engaging shore targets with their own organic kamikaze first-person-view drones and knocking Russian aircraft out of the sky with machine guns and surface-to-air missiles. In the Red Sea, the Iranian-backed Houthi rebels in Yemen have employed explosive-laden watercraft to lesser effect in response to Israel’s military campaign against Hamas in Gaza, successfully sinking the Liberia-flagged bulk carrier MV Tutor in June 2024 and consistently disrupting international maritime traffic in the region.

The concept of kamikaze boats isn’t new: The US Navy learned this lesson firsthand in October 2000, when a small boat full of suicide bombers blew a hole in the side of the Arleigh Burke-class destroyer USS Cole in Yemen’s Aden Harbor, killing 17 American sailors. But the Ukrainian and Houthi campaigns both represent weaker belligerents who have used complex attacks of missiles and drones, both airborne and maritime, to significantly disrupt their adversaries’ naval operations just as Van Riper did during Millennium Challenge decades ago.

“Within a few minutes, the US fleet was confronted with boats, cruise missiles, and aircraft, which overwhelmed the electronics and human decisionmaking,” Van Riper tells WIRED. “Small boats themselves have been demonstrated by Ukraine as useful, but to the degree they can be complemented with other systems they are even more effective.”

The US military has been steadily exploring the potential applications of USVs to naval warfare for years. Four large USVs associated with the US Navy’s Ghost Fleet Overlord initiative have been autonomously transiting oceans since at least 2018 as part of a large-scale effort to add unmanned systems to the surface fleet. In 2021, the Navy stood up Task Force 59 to “rapidly integrate unmanned systems and artificial intelligence with maritime operations” in the 5th Fleet area of operations in the Middle East, as officials announced at the time. The following year, the service established an Unmanned Surface Vessel Division to focus on building the “foundational knowledge” for the regular operation and sustainment of USVs. And in mid-2024, the service unveiled a new Robotic Warfare Specialist to focus on drone systems and stood up a separate squadron of small USVs explicitly “to deliver the most formidable, unmanned platforms in the maritime domain,” according to officials.

Commercial operators deploy Saildrone Voyager Unmanned Surface Vessels out to sea in the initial steps of U.S. 4th Fleet’s Operation Windward Stack during a launch from Naval Air Station Key West’s Mole Pier and Truman Harbor, on September 13, 2023.Photograph: Danette Baso Silvers/US NAVY

Today, USVs of all sizes are used for everything from surveillance and reconnaissance to mine sniffing, augmenting the existing surface fleet as floating sensor nodes for sailors aboard conventional warships.

The US isn’t alone in its newfound focus on drone boats. In December 2024, officials with the North Atlantic Treaty Organization (NATO) laid out plans for the alliance’s own fleet of small USVs to operate as a robotic surveillance network like “street-lighting” in busy Atlantic waterways. Then, in January, NATO’s Maritime Command announced that a contingent of 20 USVs would participate in NATO’s new Baltic Sentry operation, which is designed to safeguard sensitive communications, power cables, and other “critical infrastructure” throughout the Baltic Sea that have been the focus of sabotage efforts in recent years.

With the threat of a future conflict with China over Taiwan’s sovereignty looming on the horizon, the Navy has kicked its USV ambitions into high gear. As part of the Pentagon’s ongoing Replicator initiative launched in 2023 to quickly field both low-cost (“attritable,” in US military speak) unmanned systems to US troops abroad ahead of the next big war with a “near-peer” adversary like Russia or China, the Navy has pursued the rapid production of swarms of small, networked USV “interceptors” through its Production-Ready Inexpensive Maritime Expeditionary (PRIME) Small Unmanned Surface Vehicle (sUSV) project. These interceptors are capable of “loitering in an assigned operating area while monitoring for maritime surface threats, and then sprinting to interdict a noncooperative, maneuvering vessel,” as the Defense Innovation Unit solicitation described them.

It’s unclear what those future interceptors may look like, but the Navy and Marine Corps have in recent years experimented with various armed USVs designed to engage adversary surface fleets with lethal payloads. They include the Textron Systems–produced Expeditionary Warfare USV armed with a .50 caliber machine gun and AGM-114 Hellfire missile system the Navy publicly debuted in August 2019; the Common Unmanned Surface Vehicle (CUSV) armed with a .50 cal for force protection Textron demonstrated in 2020; the Marine Corps’ Long Range Unmanned Surface Vessel (LRUSV) outfitted with a launcher for multiple Uvision Hero-120 loitering munitions the service debuted in May 2023; and the MARTAC T38 Devil Ray which successfully destroyed several seaborne targets with Lethal Miniature Aerial Missile System–launched loitering munitions during the Navy’s first two Digital Talon exercises in late 2023. In addition, the Navy’s fiscal year 2024 budget request sought to fund an experiment to test a notional Multi-domain Area Denial from Small-USV (MADS), an unmanned Global Autonomous Reconnaissance Craft outfitted with surface-to-air FIM-92 Stinger missile launchers designed to defend larger vessels against airborne attacks.

“During future conflicts, US and allied forces will be greatly outnumbered by peer or near-peer competitors in both tactical platforms and munitions,” as the Navy’s budget documents described the logic behind the MADS experiment. “Large numbers of small, low signature, attritable unmanned missile launching vessels have the potential to improve surface force magazine depth and reduce risk to force in denied areas.”

A Lethal Miniature Aerial Missile System launches munitions from a MARTAC T-38 Devil Ray unmanned surface vehicle, attached to U.S. Naval Forces Central Command’s Task Force 59, during Exercise Digital Talon in the Arabian Gulf on October 23, 2023.Photograph: Chief Mass Communication Specialist Justin Stumberg/US NAVY

The Navy’s armed USV efforts appear to have culminated in Project 33, a new initiative unveiled as part of Chief of Naval Operations Admiral Lisa Franchetti’s 2024 Navigation Plan in September 2024 that focuses on, among other targets, “scal[ing] robotic and autonomous systems to integrate more platforms at speed” in an ostensible complement to the Pentagon’s larger Replicator effort, designed to outfit American fleets with armed robot boats ahead of a potential future war with China.

“This Navigation Plan drives toward two strategic ends: readiness for the possibility of war with the People’s Republic of China by 2027 and enhancing the Navy’s long-term advantage,” as Franchetti wrote at the time. “We will work towards these ends through two mutually reinforcing ways: implementing Project 33 and expanding the Navy’s contribution to the Joint warfighting ecosystem … By 2027, we will integrate proven robotic and autonomous systems for routine use by the commanders who will employ them.”

The Defense Department seems confident that the Navy’s robotic push will help prepare the US military for the possibility of war with China, but some seasoned military and defense observers have their misgivings. Van Riper points to Marine Corps’ Force Design 2030, a reorganization of the service ahead of a notional island-hopping conflict against China in the Pacific, as evidence that the Pentagon still hasn’t learned the right lessons from Millennium Challenge 2002.

The Marine Corps “was known for being an air-ground combined arms rapid-response deployed around the world,” Van Riper tells WIRED. “Now it has divested itself of every element of combined arms or reduced it, getting rid of its armor, breaching vehicles, mine clearing, and assault bridging capabilities, cutting its infantry and aviation, all to buy missiles and go on the defense in the Pacific. The Marine Corps got rid of existing capabilities in favor of unproven or undelivered capabilities.”

Indeed, the US military’s propensity to fixate on next-generation technology like drone boats as a one-size-fits-all combat solution may obscure those tactical lessons in combined arms evident in the Ukrainian campaign in the Red Sea, Van Riper says.

“You shouldn’t take the use of drones in isolation with what Ukraine is doing,” Van Riper says. “We presented the Navy fleet [in Millennium Challenge 2002] with multiple challenges, which is really what combined arms is. What you’re doing is presenting the enemy with a dilemma: If he tries to protect himself against threat A, he’s vulnerable to threat B, and with threats C, D, and E, he’s unable to handle it. In Ukraine, boats plus missiles and aircraft are more difficult for the Russians to respond to.”

“I’m not sure the US military today is equipped to learn from those things,” he adds. “I’m depressed from the leadership on all levels, particularly the naval services.”