The Pentagon released its annual nuclear posture review last January, outlining the nuclear capabilities of foreign nations, particularly those that pose a threat to the safety and security of the United States. To the surprise of defense experts everywhere, a long-rumored Russian “doomsday” weapon, the Ocean Multipurpose System Status-6, found its way into the document, suggesting that U.S. Intelligence officials had finally confirmed the weapon’s existence.

Prior to that day, Russian leaks had suggested Moscow was developing a massive nuclear weapon with an unusual mode of delivery, but like most information “leaked” to the Russian media for marketing purposes, the weapon was awarded little in the way of legitimate attention. Last January’s revelation that the Status-6, which goes by the name “Kanyon” within the Pentagon and “Poseidon” within the Kremlin, could soon enter service with the Russian military raised more than eyebrows. This new weapon is like nothing ever seen before in a number of ways.

What makes it different from previous nuclear weapons?

Unlike nuclear missiles, Russia’s Poseidon is a submersible drone that can be deployed from one of Russia’s stealthy nuclear attack submarines. From there, the drone could traverse thousands of miles on its own before coming to rest on the floor of an American port. Once it received the command to detonate, the massive nuclear weapon on board would produce an explosion larger than any ever recorded, resulting in a massive tsunami of irradiated water ushering destruction for hundreds of miles inland. Defending against such a stealthy nuclear attack, it’s important to note, may be beyond America’s current defensive capability — something Moscow made sure to point out in its statements this week.

“Russia will soon deploy an underwater nuclear-powered drone which will make the whole multi-billion dollar system of U.S. missile defense useless,” MK.ru said, according to a BBC translation. “An explosion of the drone’s nuclear warhead will create a wave of between 400-500 meters (1,300-1,600 feet) high, capable of washing away all living things 1,500 kilometers (932 miles) inland.”

How powerful is it?

Perhaps the most interesting part of Russia’s recent statements regarding the weapon are new claims of a 200-megaton yield. Previous rumors had placed the Poseidon at around 100 megatons, which would already be twice as powerful as the largest nuclear weapon ever detonated in history. The new 200-megaton figure, however, makes the weapon four times more powerful than the 50-megaton Tsar Bumba Russia detonated in 1961.

To give you a sense of the magnitude of this weapon, if Russia’s Poseidon truly does house a 200-megaton nuclear weapon, it would produce an explosion roughly 15,000 times more powerful than the bomb the United States dropped on Hiroshima, Japan in World War II.

While the United States has gradually shifted its nuclear strategy toward the tactical use of weapons to mitigate foreign nuclear arsenals, the Poseidon hearkens back to the concept of “total war,” in which the intent would be to deliver as much destruction and loss of human life as possible to one’s enemy, rather than to simply force surrender. Detonating a 200-megaton nuclear weapon in New York harbor would kill millions, with no distinguishing between combatants and non-combatants. In fact, this weapon would almost certainly kill far more civilians than it would service members if detonated in most major American ports.

“It’s an insane weapon in the sense that it’s probably as indiscriminate and lethal as you can make a nuclear weapon,” Hans Kristensen, the director of the Nuclear Information Project at the Federation of American Scientists, told Business Insider.

Does this give Russia any real advantage?

If Russia’s goal is Bond villainy, a weapon of this sort could certainly be used to hold a city hostage in exchange for whatever Bond villains are always after, but in reality, this massive nuclear weapon doesn’t actually change much in any diplomatic environment short of an already-global nuclear catastrophe. While the Poseidon would deliver previously unseen amounts of destruction to a coastal city, it would not neuter America’s ability to respond. Russia maintains a larger stockpile of nuclear weapons than the United States, but America still possesses more than enough firepower to utterly decimate the entire Russian nation — a fact of which the Kremlin is well aware. In fact, Russia already maintains far more powerful nuclear weapons than the United States — to no actual benefit.

Mutual assured destruction, or the concept of maintaining a diverse and hardened nuclear arsenal to ensure an equally-destructive response could be mounted after any nuclear attack, has staved off nuclear war for decades — and America’s nuclear triad remains intact, despite its advanced age. Poseidon may offer Russia a good bang for its doomsday buck, but the weapon itself would not usher in doomsday alone. The immediate nuclear response and ensured exchange of ICBMs, on the other hand, certainly would.

And nobody wins an extinction-level event.