Vladimir Putin has the Russian military on nuclear alert in response to Western sanctions over Russia’s invasion of Ukraine. But what does that mean in terms of numbers? Russia has the most warheads deployed — 1,625 — of any nuclear power other than the US. What’s more, the Russians could soon become the second country after the US to store nukes in another country. Belarus, a top Russian ally, recently tweaked its constitution to allow this. Here's a look at which nuclear powers have warhead stockpiles — and who's ready to use them.