"The supreme art of war is to subdue the enemy without fighting"

~ Sun Tzu

Why didn't Russia deploy amphibious forces to the shores of Odesa in the spring of 2022? At that point, Russians confronted the failure of the drive to Kyiv and challenges along a long front. A potential landing might have turned a flank or presented hard choices to Ukrainian leaders. Unarmed with first-hand evidence of Russian decision-making but well-served by hindsight, the authors assess that the amphibious flanking attack didn't happen because it was infeasible.

Ukrainian maritime defenses were unexpectedly effective. Sustaining forces ashore would be precarious. Isolated Russian troops ashore would be more liability than asset, and so the expected payoff from any landing was low. Russian commanders faced an acute area denial challenge.

Amphibious warfare strategy, it seems, is in need of some exploration because, after a deterrence failure in February 2022, Ukraine used tools of sea denial to deter the Black Sea Fleet from an amphibious landing in March.

This snapshot raises a question and points to an answer. What can you do with amphibious forces given current area denial, especially sea denial, measures; particularly in Europe? Those tools of sea denial mean that fouling the waters is easy but clearing them is hard. Because of this, sea denial is easier today and sea control is growing more challenging. Threats to large landing ships make traditional amphibious assaults - called forcible entry operations in the American vernacular - riskier.

Simply using amphibious forces to do ground operations in a new patch of land is too hazardous. On the other hand, a divergent model has promise to contribute to sea control.

Concepts designed for the Indo-Pacific have value in Europe

Specifically, deploying multiple, distributed, mobile cohorts of NATO marines ashore will support a broader effort. To gain and maintain sea control will be long, resource intensive, and entail a complex mix of complementary measures. In Europe, NATO can marshal potent amphibious tools, but will need new employment models to use them effectively. The traditional model expects a methodical sequence of actions to set conditions for landing.

A new "outside-in" model uses small landing forces preemptively to establish sea and archipelagic denial. This is most valuable for deterrence, but counts also as insurance in case that deterrence fails.

Four factors have the most impact on how allied amphibious forces can operate in today's operational environment:

1. First is the spread and variety of threats to maritime transit. Ukraine's successful strikes on Russia's Black Sea Fleet and the Houthis' parried attempts to disrupt Red Sea commerce illustrate the same point. The latent potential to strike ships at sea is widespread. Beneath the surface and out of view, sea mines, torpedoes, and other nefarious but subtle instruments of destruction or disruption abound.

2. Second, an accident of geography places many key geopolitical flashpoints of today along narrow waterways. Any list of potential triggers for major armed conflict between defenders of the current order and its challengers includes territory adjacent to narrow or enclosed waterways such as the Mediterranean, Black, or Baltic Seas.

Regardless of where an adversary might strike, be it in Lithuania, Taiwan, or the contested territories of the South China Sea, maintaining sea control will be critical to defense. Consider that Finland relies on maritime transit for 90% of its imports and exports.

3. Third, NATO's two newest members, Finland and Sweden, have mature and hardened capabilities to frustrate aggressive maritime harassment and targeting. Integrating such skills is a key advantage of their accession.

4. Fourth, sophisticated defenses against aircraft and missiles are possible but costly. What we've seen in the past year in the skies over Kyiv, Tel Aviv, and the Red Sea is that air and missile defense is feasible but no...