The main spokesman for Russian President Vladimir Putin has admitted that Russia has yet to achieve any of its military objectives in Ukraine and has refused to rule out the use of nuclear weapons.

Dmitry Peskov again refused to rule out using nuclear weapons against what Moscow considered as a “existential threat” in an interview with CNN on Tuesday. When asked under what circumstances Putin would deploy Russia’s nuclear capability, Peskov responded, “if it is an existential threat for our country, then it can be.”

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When asked what Putin believed he had accomplished in Ukraine thus far, Peskov responded, “Well, first of all, not yet. He hasn’t achieved it yet.”

The spokesman also said that Russia’s “special military operation” – the Kremlin’s official euphemism for its invasion of Ukraine – was “going on strictly in accordance with the plans and the purposes that were established beforehand.”

 Russia is reported to have the world’s largest nuclear arsenal, with a total of 4,477 nuclear warheads (of which 1,912 are thought to be tactical nuclear weapons).

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Tactical nuclear weapons are designed to be used on the battlefield, whereas strategic nuclear weapons are designed to be used to attack strategic targets such as cities. In practise, the only significant variation between them is the delivery system. Tactical nuclear weapons are delivered by artillery, short-range ballistic missiles, cruise missiles, or tactical aircraft.

Given their emphasis, they may have lower explosive yields than strategic weapons, however this is not always the case. The majority of modern tactical nuclear warheads have significantly more destructive force than the nuclear bombs unleashed on Hiroshima and Nagasaki by the United States during WWII.

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Tactical nuclear weapons, on the other hand, would be capable of blowing huge, deep holes in opposing lines. As such, they might aid a breach of Ukrainian defences or give a means of destroying critical targets such as airfields or important staging areas.

It would be difficult to identify preparations for such an attack. Many of Russia’s weapon systems are “dual-capable,” which means they can deploy both conventional and nuclear weapons.

What is unknown is how the West would react if nuclear weapons were used. While there would be justifiable outrage, it may likely prevent the West from further involvement in order to avert a full-fledged nuclear conflict.