Vladimir Putin's claim Russia now has "invincible" weapons that can strike anywhere in the world is probably true, experts say.
On Friday (NZ time), the Russian President said Moscow's new weapons could strike anywhere in the world, and evade missile defence shields.
"They need to take account of a new reality and understand that everything I have said today is not a bluff."
But how? Missile defence expert Laura Grego explained to Livescience's Rafi Letzter that Russia's new nuclear arsenal is largely not of the ballistic missile variety.
"Ballistic missiles, true to the name, go on a ballistic trajectory," she told the site on Monday (NZ time). "They use these powerful engines to get themselves moving really fast, but after the engines burn out they're just coasting."
It's not hard to figure out where a ballistic missile is going to land, she explains, so it's not hard to shoot them out of the sky.
Russia's new weapons evade defences in three ways. The first is by attaching nuclear warheads to cruise missiles, which don't coast to their destination high up in the air - they fly close to the ground, out of radar's sight.
"In theory, a cruise missile carrying a nuclear bomb could slip under American defenses and detection systems, and detonate before Americans could mobilise a response," wrote Mr Letzter.
And being nuclear-powered, the missiles in theory have enough power to travel across the world.
The second method is a new nuclear torpedo, difficult to detect before it detonates on the coast.
The third is a traditional ballistic missile with a deadly difference.
"A missile that can deploy multiple warheads, all of which enter the atmosphere at hypersonic speeds - up to 20 times the speed of sound - and could perform evasive manoeuvres in flight before striking their targets," writes Mr Letzter.
Dr Grego said the escalation in missile technology is a partly a result of the US abandoning the Anti-Ballistic Missile Treaty in 2001 - part of which disallowed states from building missile defence shields for this very reason.
"By building a defence, rather than discourage your adversary, your adversary is likely to just build more so that they can get up and over your defence. And then you build more defence. So it's an arms race cycle."
Former adviser to US Presidents and nuclear weapons expert Philip Coyle told Livescience much the same thing.
"In 2004, Putin himself warned the United States that if we kept going the way we were going, this is what he was going to do. And he did it."
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Mr Putin's US counterpart, Donald Trump, has called for the US to build more nuclear weapons.
In January, a group of scientists said the world was inching closer to 'Doomsday' thanks to North Korea's nuclear programme and Mr Trump's aggressive rhetoric.