There have been four iterations of the Delta-class submarines, designed to serve as a key element of the Soviet Union’s nuclear deterrence strategy.
At the height of the Cold War between the United States and Soviet Union, the Soviet Navy went on a building spree of lethal nuclear submarines. One such submarine was the Delta class, a series of nuclear-powered ballistic missile submarines (SSBNs).
The Delta-class submarines emerged in the late 1960s and 1970s as a response to the evolving demands of the Cold War arms race. The Soviet Union sought to counter the United States’ growing fleet of Ohio-class SSBNs, which were equipped with advanced Trident missiles. The predecessor to the Delta-class, the Yankee-class submarines, carried shorter-range missiles that required the vessels to operate closer to enemy shores, making them vulnerable to detection and attack.
To address this limitation, the USSR initiated Project 667B (Delta I) under the Rubin Design Bureau, aiming to develop a new generation of submarines capable of launching longer-range missiles from safer distances.
The Delta-class submarines were designed to carry the R-29 family of submarine-launched ballistic missiles (SLBMs), which offered significantly greater range and accuracy compared to earlier Soviet systems. This allowed the Delta-class subs to patrol what are known as “bastion” areas—protected waters near Soviet territory, such as the Barents Sea and Sea of Okhotsk—while still posing a credible threat to targets in North America and Europe. The development of the Delta-class reflected the Soviet Union’s broader strategy of ensuring a survivable second-strike capability, a key pillar of mutually assured destruction (MAD).
As noted above, there are four Delta-class submarine variants.
The Delta-I Class (Project 667B Murena)
Introduced in 1972, the Delta I-class submarines were the first of the series, with 18 boats constructed. These subs displaced 10,000 tons submerged, and carried 12 R-29 SLBMs, each with a range of about 4,847 miles.
The Delta I-class was powered by two pressurized water reactors, enabling a maximum submerged speed of 25 knots. Its design prioritized missile capacity over stealth, resulting in a relatively noisy acoustic signature compared to Western counterparts.
The Delta-II (Project 667BD Murena-M)
Entering service in 1975, the Delta II-class was an extended version of the Delta I-class, with four boats built. The hull was lengthened from the original and could accommodate 16 R-29D missiles, increasing the submarine’s strategic payload.
Despite this upgrade, the Delta-II retained many of the same systems as its predecessor, including its propulsion and sonar, limiting its benefits to the Kremlin.
The Delta-III (Project 667BDR Kalmar)
Commissioned starting in 1976, the Delta-III marked a significant advancement, with 14 units produced. These submarines carried 16 R-29R missiles, capable of delivering multiple independently targetable reentry vehicles (MIRVs), which allowed a single missile to strike multiple targets.
Perhaps more interestingly, the Delta-III also featured improved fire control systems and quieter propulsion, enhancing its survivability. Its displacement grew to around 10,600 tons submerged, reflecting the increased missile capacity and upgraded electronics.
The Delta-IV (Project 667BDRM Delfin)
The final and most advanced variant, the Delta-IV, entered service in 1984, with seven boats built Equipped with 16 R-29RM (later R-29RMU Sineva) missiles, the Delta-IV offered a range of over 5,100 miles and greater accuracy. Upgrades included enhanced sonar, improved quieting technologies, and a more robust hull design. The Delta-IV remains in service with the Russian Navy as of 2025, underscoring its enduring reliability and strategic value.
All Delta-class submarines were equipped with torpedoes and anti-submarine missiles for self-defense, as well as advanced navigation and communication systems for long-duration patrols. Their double-hulled construction, with an outer lightweight hull and an inner pressure hull, provided resilience against depth charges and collisions, while their nuclear propulsion allowed for extended deployments without refueling.
The Delta Fleet’s Operational History
Russia’s Delta-class submarines were deployed primarily by the Soviet Northern Fleet and Pacific Fleet, conducting deterrence patrols in strategic bastions to minimize exposure to NATO anti-submarine warfare (ASW) forces. Their ability to launch missiles from submerged positions in Arctic waters or near Soviet coastal regions made them a formidable component of the Soviet nuclear triad, alongside land-based ICBMs and strategic bombers.
During the Cold War, Delta-class submarines were involved in numerous high-stakes operations, including tracking NATO naval exercises and maintaining a constant presence in key maritime regions. Their patrols were shrouded in secrecy, but incidents such as the 1986 collision between a Delta-I submarine and the USS Augusta in the Atlantic highlighted the tense cat-and-mouse games played between Soviet and Western navies.
After the dissolution of the Soviet Union in 1991, the Delta-class submarines faced challenges due to funding shortages and maintenance issues. Many Delta-I and Delta-II boats were decommissioned in the 1990s, while the Delta-III and Delta-IV fleets were prioritized for modernization.
The Delta-IV, in particular, underwent significant upgrades in the 2000s, including the integration of the R-29RMU Sineva and later the R-29RMU2 Layner missiles, ensuring its relevance in the post-Cold War era.
The Delta-class submarines left an indelible mark on naval warfare and strategic deterrence. By providing the Soviet Union with a survivable and flexible platform for nuclear missile delivery, they helped maintain a delicate balance of power during the Cold War. Their development spurred advancements in submarine technology, including missile guidance, propulsion, and stealth—influencing designs like the Borei-class submarines that are now the backbone of Russia’s SSBN fleet.
The Delta-class submarines also underscored the importance of naval forces in nuclear strategy. Unlike land-based missiles, which are vulnerable to preemptive strikes, SSBNs like the Delta-class offered a hidden and mobile launch platform, ensuring a credible second-strike capability.
Early variants of the Delta-class suffered from noisy acoustics, making them easier to detect by advanced Western ASW technologies. Additionally, the high cost of construction and maintenance strained Soviet and later Russian naval budgets, particularly during the economic turmoil of the 1990s.
As a symbol of Cold War engineering and strategic resolve, the Delta-class submarines remain a fascinating subject for historians, naval enthusiasts, and policymakers alike.
About the Author: Brandon J. Weichert
Brandon J. Weichert, a Senior National Security Editor at The National Interest as well as a contributor at Popular Mechanics, who consults regularly with various government institutions and private organizations on geopolitical issues. Weichert’s writings have appeared in multiple publications, including the Washington Times, National Review, The American Spectator, MSN, the Asia Times, and countless others. His books include Winning Space: How America Remains a Superpower, Biohacked: China’s Race to Control Life, and The Shadow War: Iran’s Quest for Supremacy. His newest book, A Disaster of Our Own Making: How the West Lost Ukraine is available for purchase wherever books are sold. He can be followed via Twitter @WeTheBrandon.
Image: Shutterstock / Sergei Fokin.
