Poseidon: The Ultimate Weapon of Vengeance [i]

“To wipe out the enemy coast…”

Very long article, with excellent illustrations.

Black Mountain Analysis Mike Mihajlovic, Nov 10, 2025

A weapon system on its own

The Poseidon, designated 2M39 in Russian service and known to NATO as Kanyon, is among the most enigmatic and controversial strategic systems developed in recent years. It resists conventional classification: neither a conventional torpedo nor a crewed submarine, it represents a novel class of autonomous, nuclear-powered underwater vehicle designed to carry a nuclear warhead.

This autonomous, nuclear-powered underwater vehicle, formerly designated Status-6, has been described in open sources as capable of carrying a very large thermonuclear warhead (some reports even cite yields as high as 100 megatons)1 and of transiting intercontinental distances at depths that would place it beyond the reach of most conventional antisubmarine weapons, arguably leaving only exceptionally large-yield nuclear depth charges as a theoretical counter. Open reporting also suggests it can adopt multiple mission modes: a high-speed transit phase at depth, which offers rapid repositioning but is more readily detectable by advanced acoustic sensors, and a prolonged low-speed, low-observability cruise that exploits nuclear endurance to remain submerged for effectively indefinite periods before conducting a final approach to a target.

As with many novel Russian weapons, most technical details remain classified; nevertheless, a synthesis of open-source analysis and official Russian statements permits a broad—albeit uncertain—reconstruction of Poseidon’s design philosophy, capabilities, and potential strategic effects.

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In summary, the Poseidon system represents a technically feasible but strategically extreme extension of known nuclear and naval technologies. It most likely uses a compact liquid-metal-cooled fast reactor to achieve long-range, high-speed operation at great depths, carries a warhead of 2-100 Mt, and could inflict catastrophic local damage and contamination on any coastal target. Yet the notion that it could raise ocean-wide radioactive tsunamis is unsupported by physical science. Its true significance may lie less in its physics than in its symbolism: a weapon designed to project the image of ultimate deterrence by threatening entire coastal societies, even if the practical mechanics of such annihilation are more limited than popular imagination suggests.

Politically, the deployment of Poseidon adds a new dimension to strategic deterrence. Its autonomous nature and perceived “doomsday” capability suggest a weapon intended more for psychological and geopolitical signaling than for practical battlefield use. Its mere existence challenges traditional arms control frameworks and complicates stability calculations by introducing a new underwater axis of nuclear deterrence.

Despite the growing public literature, many details remain unknowable. The reactor’s design, actual performance, warhead configuration, and even deployment status are tightly held secrets. Modeling the hydrodynamics of a multi-megaton underwater detonation is inherently uncertain, as no full-scale tests have ever been conducted at such yields or depths. Extrapolations from smaller historical tests provide useful guidance but cannot capture all nonlinear effects of deep-water bubble dynamics or coastal interactions. Moreover, the strategic intent behind Poseidon, whether as a second-strike deterrent, a terror weapon, or an anti-access denial system, remains speculative and politically sensitive. https://bmanalysis.substack.com/p/poseidon-the-ultimate-weapon-of-vengeance?utm_source=post-email-title&publication_id=1105422&post_id=177880124&utm_campaign=email-post-title&isFreemail=true&r=1ise1&triedRedirect=true&utm_medium=email