US Navy's Ohio-class submarines offer unparalleled firepower in uncertain times

The US Navy's Ohio-class submarines are among the most powerful submarines in the world, and would significantly enhance the US global posture and help achieve surprise in a potential conflict in the Arabian Sea, where tensions have been simmering.

The largest submarines ever built by the US Navy, the Ohio-class includes 14 ballistic missile submarines (SSBNs) and four cruise missile submarines (SSGNs).

The SSBNs serve as an undetectable launch platform for intercontinental missiles, and are designed for stealth and the precise delivery of nuclear warheads, according to the Navy.

SSBNs are specifically made for extended deterrent patrols, and make up one leg of the US nuclear triad, which also includes land-based intercontinental ballistic missiles (ICBMs) and land-based long-range bombers.

The SSBNs' basic mission is to remain hidden at sea with their submarine-launched ballistic missiles (SLBMs) and deter a nuclear attack on the United States by another country by ensuring second-strike capability.

At any given moment, some of the Navy's Ohio-class submarines are conducting nuclear deterrent patrols.

The submarines are designed with three large-diameter logistics hatches that allow sailors to rapidly transfer supplies and equipment to cut down on the amount of time required for replenishment and maintenance.

The Ohio-class submarines can operate for 15 or more years between major overhauls. On average, they spend 77 days at sea followed by 35 days in-port for maintenance.

Each SSBN has two crews, Blue and Gold, which take turns manning the submarines.

"This maximizes the SSBN's strategic availability, reduces the number of submarines required to meet strategic requirements, and allows for proper crew training, readiness and morale," according to the Navy.

The Ohio-class SSBNs "may be the most destructive weapon system created by humankind", wrote Sebastien Roblin for the National Interest in 2021.

Each of the SSBNs originally carried up to 24 SLBMs with multiple, independently-targeted warheads.

Under provisions of the New Strategic Arms Reduction Treaty, each submarine has had four of its missile tubes permanently deactivated and now carries a maximum of 20 missiles.

The SSBN's strategic weapon is the Trident II D5 missile, "... which can be fired from underwater to strike at targets more than 7,000 miles [11,265 km] away depending on the load", Roblin wrote.

"As a Trident II re-enters the atmosphere at speeds of up to Mach 24, it splits into up to eight independent re-entry vehicles, each with a 100- or 475-kiloton nuclear warhead."

A full salvo from an Ohio-class submarine can be launched in less than one minute, he noted.

"The current plan is to keep 12 Ohio-class subs active at time with 20 Trident IIs each, while two more [SSBNs] remain in overhaul, keeping a total of 240 missiles active at a time with 1,090 warheads between them."

Cruise missiles

The 1994 Nuclear Posture Review found that the United States needed only 14 of its 18 SSBNs to meet its strategic force needs, prompting the Navy to transform four Ohio-class submarines into conventional land attack and special operations forces (SOF) platforms.

The conversion of the four submarines was completed in 2007.

For their part, the Ohio-class SSGNs can carry up to 154 Tomahawk cruise missiles, the equivalent of what is typically deployed in a surface battle group.

The Tomahawk cruise missiles themselves have a 1,000-mile [1,609 km] range.

The SSGNs can also be configured to host up to 66 special operations personnel, such as US Navy SEALs.

As part of the conversion, the two forward-most missile tubes were permanently converted to lock-out chambers that allow clandestine insertion and retrieval of SOF personnel.

Each lock-out chamber can also accommodate a Dry Deck Shelter (DDS), a removable module that can be attached to the SSGN to allow divers to leave and enter easily while the boat is submerged.

Each SSGN also received the Common Submarine Radio Room and two High-Data-Rate antennas for significantly enhanced communication capabilities.

This enables each SSGN to serve as a forward-deployed, clandestine Small Combatant Joint Command Centre.

The Arabian Sea

As Russia's unprovoked invasion of Ukraine continues to cause many repercussions around the world, including soaring energy costs and increasing world famine, it also indirectly strengthened the US military's ability to operate in the Indian Ocean, and in particular, the Arabian Sea.

North Atlantic Treaty Organisation (NATO) allies have ramped up patrols in waters normally handled by the US Navy, enabling the United States to put a greater focus on the Indian Ocean.

The expected ascension of Sweden and Finland into NATO will also add their naval arsenals to the communal defence posture and lighten the US Navy's load in Europe.

Just placing one Ohio-class submarine in the Arabian Sea would significantly enhance the US global posture and help achieve surprise in a conflict.

The Arabian Sea has seen its strategic importance grow in recent years.

It is the waterway that all Iranian ships must pass to reach world ports, and a key link in China's "string of pearls".

China's massive infrastructure drive to connect its mainland to the Horn of Africa via a network of military and commercial facilities in recent years has raised concerns.

Its sea lines run through major maritime choke points including Bab al-Mandeb Strait at the entrance to the Red Sea; the Strait of Malacca, between the Indian and Pacific oceans; the Strait of Hormuz, at the entrance to the Persian Gulf; and the Lombok Strait, between the islands of Bali and Indonesia.

Beijing's global infrastructure drive, known as the Belt and Road Initiative (BRI) or One Belt, One Road (OBOR), continues inland, reaching other parts of the Middle East, Central Asia and Africa.

China's ostensibly commercial projects serve a dual purpose, allowing for its rapidly growing military to expand its reach, warn critics.

Ohio-class SSGNs and their Tomahawk missiles could play a major role in a potential conflict in the Arabian Sea and the surrounding region.

For reference, the distance from the centre point of the Arabian Sea to Tehran, Iran, is 1,035 miles (1665 km).

Iran has long threatened to close the Strait of Hormuz and attack maritime vessels in the event of war.