Russian President Vladimir Putin has triggered considerable concern after placing the country’s nuclear forces in a “special mode of combat duty”, suggesting they were moving up a level on the escalation ladder.
The problem is that there is little understanding about what this means in practice for Russia’s Strategic Rocket Force arsenal of 6,400 nuclear warheads.
In nuclear terminology it is a phrase not previously used by the country, which has the largest nuclear stockpile in the world.
Unlike the US, with its “defence ready condition” running from the lower level of “Defcon Five” to the highest, which suggests impending nuclear attack, of “Defcon One”, Russia does not appear to have a similar structured approach.
During peacetime — to avoid an accidental or rogue firing — the Russian launch process is similar to an electric circuit in that it is disconnected making use impossible.
But it is possible that Mr Putin’s words lead to the wires being connected, so that if he gives the order for a strike then it will be immediately carried out.
Part of the problem, defence experts say, is that, bar an incident in 1983, the world has not previously reached this serious juncture.
What it does mean is that Nato’s intelligence surveillance will intensify to examine whether there are signs of nuclear escalation.
Russia has four different methods of delivering its weapons of mass destruction. Hundreds of InterContinental ballistic missiles and are stationed in silos around the country, making any escalation there difficult to track.
Instead the West’s monitoring systems will be tracking Russia’s nuclear armed Typhoon or Borei SSBN submarines very closely to see if some are being hurried out of port to join at least one already deployed.
Following its “Scud-hunting” experience in Iraq in 1991 and 2003, and with Iran’s worrying missile developments, the US has a greater ability to track mobile rocket launchers.
A key escalation will be whether Russia has gone into a “dispersal” mode whereby its RS-24 Yars missiles carried on massive 18-wheel lorries disappear into forests or urban areas.
Russia has about 180 of the mobile launchers making tracking and targeting difficult for each missile which carries up to 10 warheads and has a range of 12,000 kilometres.
Intelligence analysts will also examine near-real time footage of Russia’s airfields to see if nuclear convoys from ammunition dumps are arriving to “bomb-up” the air force’s nuclear capable strategic bombers such as the Tu-160 Blackjack.
A sign of serious nuclear intent would be observing the painstaking task of getting nuclear bombs on board the aircraft.
“The problem is we've not really come this far in the nuclear scenario,” said Russia military expert Sam Cranny-Evans of the Rusi think tank. “We've not got to that next level of escalation before, so anything after that is enormously risky, therefore the Russians have to be very certain that this move is going to provide some sort of return.”
In 2010 Russian updated its military doctrine stating nuclear weapons would be launched “in response to the use of nuclear weapons” or WMDs.
But more pertinent to the Ukraine conflict is the suggestion that the warheads would be fired “in case of aggression against Russia with the use of conventional weapons when the very existence of the state is threatened”.
In this line of thinking by the experts Russia would initiate a limited nuclear exchange to make its foes negotiate for peace. Some fear that could be the threat Mr Putin is raising.
“This has to be taken more seriously than in the past,” said Russia expert Keir Giles at the Chatham House think tank. “Because if President Putin realised that on this occasion he's actually dealing with a potential major setback in Ukraine, given his retreat from reality that might give him more of an incentive to do something with incomprehensible deadly consequences.”