On the Eve of Obstruction—Countering Blockship Attacks

Blockship attacks entail obstructing key waterways by deliberately scuttling ships, running them aground, or having them impale themselves onto infrastructure. Such attacks could delay maritime movements in U.S. or key overseas ports, affecting all U.S. military services and potentially disrupting billions of dollars in commerce. The impact could be especially severe if multiple ports were targeted simultaneously, or if the attacks were compounded by large environmental effects or the use of naval mines or other weapons.

In this paper, the authors examine the threat of blockship attacks in key U.S. waterways, current and potential measures to reduce the risk of an effective blockship attack, and ways of reducing an attack’s impact by accelerating post-attack clearance. The vulnerability of U.S. military forces and civilian commerce to blockship attacks is a significant concern, particularly given the large sizes of modern cargo ships relative to the width of critical waterway bottlenecks, and it is crucial to inform policymakers and the wider public about the risk so that measures can be implemented to further diminish the probability and impact of these attacks.