With 18 Ohio-class submarines in the US Navy inventory, at least one is likely submerged in the deep and vast waters of the Indian Ocean, ready to play a decisive role in securing the region from any potential adversary threats.

The US Navy has two types of Ohio-class submarines: 14 nuclear-powered, ballistic missile-carrying submarines (SSBNs) and four cruise missile submarines (SSGNs), loaded with 154 Tomahawk cruise missiles each that can hit targets as far as 1,600km away.

Each SSBN can carry up to 20 Trident II D5 sea-launched nuclear ballistic missiles (SLBMs), giving the US military a combined total of 280 such missiles.

The Ohio-class SSBNs form the sea-based leg of the US strategic nuclear deterrent triad.

"The triad, along with assigned forces, provide 24/7 deterrence to prevent catastrophic actions from our adversaries and they stand ready, if necessary, to deliver a decisive response, anywhere, anytime," according to the US Department of Defence (DoD).

The US Navy's ballistic missile submarines, often referred to as "boomers", serve as an undetectable launch platform for missiles. Their stealth design makes finding them an almost impossible task, giving pause to potential adversaries.

The Ohio-class design allows the submarines to operate for 15 or more years between major overhauls, according to the DoD. On average, SSBNs spend 77 days at sea followed by 35 days in port for maintenance.

"In the past, two of the 14 submarines would be in reactor refuelling overhaul (a lengthy refitting process typically carried out about midway through their operating lifespan) at any given time," Nuclear Notebook reported January 15.

"As the last refuelling was completed in 2022, all 14 boats could now potentially be deployed until 2027," it noted.

However, because operational submarines must undergo minor repairs at times, there are likely between 8 and 10 at sea at any given time.

"Four or five of those are thought to be on 'hard alert' in their designated patrol areas, while another four or five boats could be brought to alert status in hours or days," the report said.

Strategic advantages of the Indian Ocean

While the specific location and movements of US Navy submarines are highly classified while at sea, it should be assumed that at least one is in the Indian Ocean.

One of the key strategic advantages of the Indian Ocean is its depth and vastness, which make it an ideal location for operating submarines, including SSBNs.

With an area of approximately 70 million square kilometres, the Indian Ocean is the third largest body of water in the world, and its depths reach over 7,000 metres in some areas.

This provides ample space for SSBNs to operate without detection, and also makes it difficult for potential adversaries to track their movements.

In addition to its vastness, the Indian Ocean is also known for its warm waters, which can help to conceal the signature of SSBNs.

Warm waters can create a layer of thermal distortion that can make it more difficult for sonar systems to detect submarines. This can provide a significant advantage to SSBNs, particularly when combined with other measures such as sound-absorbing coatings on their hulls.

The Indian Ocean is also home to a number of strategically important chokepoints, such as the Strait of Hormuz, the Strait of Malacca and the Suez Canal.

These chokepoints are critical for global trade, with large amounts of oil and other commodities passing through them on a daily basis.

This situation makes them a potential target for adversaries seeking to disrupt global commerce, and highlights the importance of maintaining a strong naval presence in the region.

For SSBNs, these chokepoints can also serve as potential launch locations for their ballistic missiles.

By operating in the Indian Ocean, SSBNs can position themselves near the chokepoints, providing them with a strategic advantage in the event of a conflict.

Show of force

The US Navy on Saturday (April 8) released a photograph of the USS Florida, one of the Ohio-class submarines that carry 154 Tomahawk cruise missiles, transiting the Suez Canal en route to the Red Sea.

"The submarine entered the region April 6 and began transiting the Suez Canal the following day," Cmdr. Tim Hawkins, a spokesman for US Naval Forces Central Command/US 5th Fleet, said in a statement.

The fleet's area of responsibility includes the Gulf of Oman, the Arabian Sea, the Red Sea and parts of the Indian Ocean.

The show of force follows the repositioning of the George H.W. Bush Carrier Strike Group in the Mediterranean Sea closer to the Middle East, and US airstrikes on facilities in Syria used by groups affiliated with Iran's Islamic Revolutionary Guard Corps (IRGC).

Those actions came after an unmanned drone "of Iranian origin" hit a maintenance facility on a coalition base near al-Hasakeh city, killing one US contractor and wounding five US service members.

The US Navy in December announced that the USS West Virginia SSBN had docked in October at the remote island of Diego Garcia in the Indian Ocean as part of an extended deterrence patrol.

Diego Garcia is overseas territory of the United Kingdom used by both the US and UK militaries.

Its remote location provided the nuclear-missile-equipped submarine the ability to switch out the 150-person crew unobserved by outsiders, CNN reported December 2, citing a military official familiar with the unusual port stop.

The delayed announcement of the port call serves two purposes, the report said. It gave the submarine ample time to transit to other locations in the Indian Ocean, and it sent a message to potential adversaries in the region.

"They should take from this that a ballistic missile submarine which is undetectable can operate in any ocean for an extended period," the unnamed official said.

While the official declined to specify the intended recipient of the message, the underwater stealth of US submarines is critical to gathering highly classified signal intelligence about adversaries, CNN reported.

"Every operational plan rests on the assumption that nuclear deterrence is holding, and (ballistic missile submarines) like West Virginia are vital to a credible nuclear deterrence for the United States and our allies," Adm. Charles Richard, commander of US Strategic Command, said in a statement.

Before visiting Diego Garcia, the USS West Virginia surfaced in the Arabian Sea to embark US Central Command (CENTCOM) commander Gen. Michael "Erik" Kurilla, who participated in a joint communications exercise "to validate emerging and innovative tactics in the Indian Ocean", the Navy said in a press release December 7.

"The stealth and response capability of these submarines combined with the crew's training make our SSBNs the most powerful warships in the world," said Vice Adm. William Houston, commander of Naval Submarine Forces.