On July 1, a fire on the nuclear-powered submarine AS-31 “Losharik,” killed 14 high-ranking Russian navy officers. Seven of them were captains of the first rank, the equivalent of captain in the US Navy. Three were captains of the second rank, two were captains of the third rank, and two had been awarded the order of “Hero of Russia,” the highest possible military order in Russia. The other two were a captain-lieutenant and a medical officer. The Losharik submarines are operated by the Main Directorate of Deep-Sea Research which is reporting to the Russian military intelligence agency GRU.

The vessel is considered top secret and worth an estimated $1.5 billion. Details about how it looks and what it can do have been shrouded in secrecy since its first deployment in 2003, but it is reportedly capable of carrying out high-level intelligence operations on the seafloor, including the detecting and cutting of communication and internet cables.

Information about the submarine disaster was not released until the evening of July 2. The Russian Navy has classified details about the fire as a “state secret.” Russian President Vladimir Putin called the death of the 14 officers a “big loss for the Russian navy and army.”

The fire reportedly began around 9 p.m. local time on Monday in the Barents Sea in the Russian Federation. The Russian Defense Minister Sergei Shoigu has declared that the fire began in the submarine’s battery compartment, and that the vessel, worth an estimated $1.5 billion, could be repaired and redeployed.

Reports in the newspapers Kommersant and Gazeta.Ru, both based on anonymous sources in the Ministry of Defense and military, suggested that the cause for the fire was a short circuit. According to Kommersant, it occurred in one of the electrical rooms of the underwater nuclear power station AS-31 that powered the submarine. Initially, there were conflicting reports as to whether the fire occurred on the Losharik or a potential mother submarine, the Podmoskovye.

The submarine carried a crew of 25 people. While some reports have suggested that all were navy officers, others said that one or two civilians were on board. According to the official version, the submariners died from toxic chemicals released by the fire, trying to protect a civilian and the submarine. Five survivors were later hospitalized with smoke inhalation and concussion. Ten of the fourteen bodies have not yet been recovered.

The Ministry of Defense has declared that the nuclear reactor powering the submarine had not been damaged and that no radiation had been released. Norwegian authorities found no elevated levels of radiation as of Wednesday. A report by the Norwegian Radiation Protection Authority, according to which they had been notified by the Russians of a gas explosion aboard the vessel, was denied by the Kremlin.

Why such a large high-ranking crew would be on board the submarine has not been explained.

The military columnist Alexander Golts noted, “We’re talking about a top-secret military division whose responsibilities are outside the broader considerations of the Russian army. ...It [could be] a chance to collect information: roughly speaking, they [military servicemembers] collect everything that lands on the bottom of the sea. That primarily means debris from weapons testing, which is something every agency in the world searches for. It’s also known that countries whose militaries are opposed with one another install sensors, all possible monitors, on the ocean floor to track the submarine routes of their potential opponents. There are connective cables deep on the ocean floor. If you can connect to them, you can discover quite a lot. In times of conflict, destroying those cables can destroy a potential opponent’s ability to communicate.”

A report by the Drive drew attention to the fact that the official newspaper of the Russian Ministry of Defense, Krasnaya Zvezda (Red Star), attached a hitherto unseen drawing of the newly developed Belgorod submarine, a version of the Oscar II-class submarine, to a report on the submarine disaster. It is unclear whether this in any way indicates that the Belgorod, construction for which was officially launched in April this year, was involved in the incident. The longest submarine in the world, the Belgorod is designed as the country’s first operational launch platform for the Poseidon nuclear-powered and nuclear-armed long-range torpedo.

The Poseidon reportedly has unlimited range and is difficult to detect. According to the Drive, “the weapon is meant to give Russia a second-strike deterrent capability that is entirely immune to U.S. missile defenses.” Other “special missions” for which the submarine was constructed include intelligence gathering and acting as a mother ship for smaller manned and unmanned submarines like the Losharik. Unconfirmed reports of the fire on Monday suggested that a larger mother ship, the Podmoskovye submarine, was deployed in the Barents Sea alongside the Losharik.

Monday’s submarine disaster is the third major Russian submarine disaster in less than two decades. In 2000, at least 118 died when the nuclear submarine Kursk sank after several explosions during naval exercises in the Barents Sea. In 2008, 20 people died in a gas leak on the submarine K-152 Nerpa in the Sea of Japan.

The fire is a blow to the Kremlin and the Russian oligarchy, putting into question its military capacities amidst an international military buildup, led by the US and NATO. For the working class, the Losharik disaster is a chilling reminder of the advanced state of the preparations for world war.

Whatever the exact reason for its deployment on Monday, there is little question that it was bound up with the efforts of the Russian state to prepare itself for a possible assault by the US and NATO, which could involve nuclear weapons.

Recent years have seen a massive escalation of an international arms race. Especially since the beginning of the Ukraine crisis in 2014, which was triggered by the US- and EU-backed fascist coup in Kiev, NATO, the EU and the US have aggressively built up their military in an open effort to prepare for war against Russia. Earlier this year, the US announced its withdrawal from the Intermediate Range Nuclear Forces (INF) Treaty, which prohibits the deployment of land-based missiles with ranges of up to 5,000 miles. Just last week, the US Senate approved the largest military budget in US history of $750 billion.

While the Kremlin has recently cut back on military spending, the Russian government has taken steps in recent years to modernize its army and navy in case of war.

In this arms race, submarines are playing an important role. Submarines are central to the gathering of military intelligence. Since vessels like the Losharik can detect and cut internet and other communication cables on the ground of the ocean, they can also play a central role in cyber warfare. Just last month, the New York Times revealed that the White House had secretly launched massive cyber attacks on Russia. Earlier this year, the Kremlin announced that it was preparing its own Russian internet that could function if the broader internet was shut down in case of war.

Another crucial function of nuclear submarines is that of nuclear deterrent. In 2015, Vice noted that, “Nuclear ballistic missile submarines are considered the nuclear deterrent of last resort because they’ve historically been the most reliable and best protected part of the nuclear arsenal. Even if an attacker can hit every single square inch of a country in a surprise nuclear attack, the attacker would still be vulnerable to a devastating counterattack launched by nuclear subs hiding at sea. Because of this, the majority of the US nuclear arsenal is submarine-based. A guaranteed ability to counterattack goes a long way in preventing enemies from getting an itchy nuclear trigger finger.” The report highlighted that military strategists in Washington were preparing for the possibility of “terrain-involved submarine warfare” which could involve the placing of nuclear weapons on the bottom of the sea.