The collapse of Baltimore's Francis Scott Key Bridge caused a tragic loss of life and awakened Americans to the fragility of the maritime transportation system. While this disaster appears to have been purely accidental, adversaries of the United States are likely taking note of how vulnerable a major American port could be to an attack by something as common as a cargo ship going nine miles per hour.
At least two recent events demonstrated how channels can be easily blocked by disabled ships. Russia was able to trap most of the Ukrainian fleet in port during its 2014 seizure of Crimea by sinking two antiquated ships. The accidental grounding of the Ever Given in the Suez Canal in 2021 also highlighted how obstructive one of today's giant container ships can be, and the fragility of supply chains to single points of failure.
These are all instances of blockships, a term largely associated with naval warfare, which has a broader and more unsettling implication in the context of our modern, interconnected world. Essentially, blockships entail the use of vessels, often old or already damaged, that are intentionally sunk in narrow waterways to create obstacles, impeding the movement of enemy ships.
Blockships entail the use of vessels that are intentionally sunk in narrow waterways to create obstacles, impeding the movement of enemy ships.
Share on TwitterThese are all instances of blockships, a term largely associated with naval warfare, which has a broader and more unsettling implication in the context of our modern, interconnected world. Essentially, blockships entail the use of vessels, often old or already damaged, that are intentionally sunk in narrow waterways to create obstacles, impeding the movement of enemy ships.
A series of deliberate attacks in multiple locations could have a much greater impact, trapping U.S. warships and military logistics vessels in port at the moment an aggressor attacked a U.S. ally. While obstructions could eventually be cleared with specialized Navy and Coast Guard divers and equipment, the days or weeks that might elapse could enable an aggressor to achieve victory before the full might of American power arrived.
Perhaps in conjunction with such attacks, obstructing a few major civilian ports would strain the American economy and create additional demand for scarce diving and salvage capabilities. While the flow of civilian goods can eventually be rerouted, doing so entails time, costs, and disruption. These difficulties are magnified for goods that require specific handling equipment, such as fuel and other liquids.
The deliberate use of obstructive tactics has a long history, with documented cases stretching back millennia; only a couple of features are relatively new. One is the phenomenal scale of cargo ships, the largest of which now handle eight times the capacity of those in the 1970s, and which rival the Empire State Building in size.
The other is that these ships are overseen by relatively small crews, limiting the number of personnel who need to be suborned and then potentially put at risk. At some future date, if cargo ships become wholly uncrewed, the entire operation could be done via remote control. Regardless, a massive cargo ship conducting seemingly routine movements can rapidly be transformed into a highly damaging weapon, perhaps one that is laden with booby traps to hinder its clearance.
The United States and other nations can take several steps to address the threat of obstructive attacks employing cargo ships. The first is enhancing intelligence collection and analysis regarding this threat, enabling the interception of suspect cargo as they approach U.S. waters. Unfortunately, if intelligence fails, the speed with which a cargo ship can become a high-momentum weapon likely precludes attempts to constrain its movements in the minutes before the attack. If the ship is departing a U.S. port, the threat indicators could be nearly impossible to detect, much the same as an inside threat.
The remaining steps, therefore, entail accelerating reaction timelines. Despite budgetary pressures, there is a need to continue to invest in frequently updated, detailed characterizations of the seabed in essential channels to aid in response to such episodes. Knowledge of the seabed composition and precise depths, as well as documentation of the precise positioning of undersea infrastructure and detritus, can improve recovery timelines after attacks involving blockships or naval mines, as well as after earthquakes or hurricanes.
The number of trained divers and other response personnel, and the quantity of equipment for salvage, can also be increased over time. Such equipment can also be qualitatively enhanced: for example, ever-improving uncrewed undersea vehicles can aid in exploring the wreck and even remediating it.
Finally, tabletop and live exercises should be held to improve coordination and collective effectiveness. Participants in these exercises should include the Coast Guard, Navy, and other military services, as well as the intelligence community, state and local authorities, and representatives from the Departments of Transportation, Commerce, and Homeland Security. Whenever possible, allied military units that can also contribute to recovery should also be involved.
A purposeful collision or scuttling is no longer an unforeseen threat but is emerging as a “grey rhino”—a threat that is predictable but is not addressed in advance.
Share on TwitterHistorically, the idea of a deliberate bridge collapse, akin to a blockship, has been considered a black swan event—an unpredictable, rare scenario with severe ramifications. However, the evolving landscape of global shipping, characterized by larger vessels, congested waterways, and an uptick in shipping-related accidents disrupting the global supply chain, should be reshaping this perception. These factors suggest that a purposeful collision or scuttling is no longer an unforeseen threat but is emerging as a “grey rhino”—a threat that is predictable but is not addressed in advance.
The accident in Baltimore is both a human tragedy and a reminder of how an adversary could seek to close critical waterways. By taking sustained actions to prevent and respond more effectively to obstructive attacks, the United States can help mitigate the risk and protect the maritime movements on which its security depends.
Scott Savitz is a senior engineer at RAND a nonprofit, nonpartisan research institution. Michelle Ziegler is a senior technical analyst at RAND.
