A possible Crimean Crisis leading to WW3?

How would it be possible for WW3 to occur after Russian soldiers seize and take control of the Crimean peninsula in 2014? There was a huge backlash from other countries and some were even paranoid of another territory or country being taken over by Russia even though it didn't happen. But lets say each side feels more threatened and aggressive which results in higher tensions to the point where you have a huge global scale war in this alternate timeline. How could it happen and what is the result? What would happen to other countries and such as well?
 
Nothing short of Russian tanks rolling through Kiev would provoke a direct foreign intervention.

Given how quickly NATO was to balk at doing even limited direct military action against Russian moves, even that might not be enough. Ukraine just isn't worth thermonuclear war to Western/Central Europe and America...
 
Given how quickly NATO was to balk at doing even limited direct military action against Russian moves, even that might not be enough. Ukraine just isn't worth thermonuclear war to Western/Central Europe and America...
Then then leaves me to create another thread to "What if Russia really actually did invade Ukraine?".
 
The Ukraine gets mighty mad that the 'West/NATO' isn't helping with the asymmetric threat the Russians are posing, as they give up the Crimea they go the poison pill route. Either a nuclear weapon or chemical/biological weapons are left behind (during the breakup of the USSR such a misplacement could be possible, the government keeping them as a last ditch weapon is not completely ASB) and detonated nearby the Russian bases basically making the whole exercise moot for the Russians, who by the way are now enraged! Ukraine states they are innocent, all signs point to Russian weapons. NATO gets pulled in to defend them. Hi WWIII, how's it going?
 
The Ukraine gets mighty mad that the 'West/NATO' isn't helping with the asymmetric threat the Russians are posing, as they give up the Crimea they go the poison pill route. Either a nuclear weapon or chemical/biological weapons are left behind (during the breakup of the USSR such a misplacement could be possible, the government keeping them as a last ditch weapon is not completely ASB) and detonated nearby the Russian bases basically making the whole exercise moot for the Russians, who by the way are now enraged! Ukraine states they are innocent, all signs point to Russian weapons. NATO gets pulled in to defend them. Hi WWIII, how's it going?
Russia would long know about such a weapon. They long had the whole Ukrainian counterintelligence organisation in their pockets and friendly relations, barring the hiccup 2005-2010, since the end of the USSR. The Ukraine had no need for a weapon too: it's borders were supposed to be guaranteed by a cast iron treaty when it did away with nukes.
 
To be clear, NATO is NOT deliberately going to war over Crimea, or any other part of Ukraine. The only way that might happen is with Russian nuclear first-use against Ukraine. Even in that scenario, there is a high chance of both sides backing down rather than taking things to the next level, depending on who exactly is calling the shots in D.C. and Moscow.

A NATO-Russia conflict on anything more than a border skirmish level would be the most destructive conflict of the 21st Century. We're talking about Russian troops and soldiers from NATO countries, with both sides equipped with 4th and 5th generation fighters, strategic bombers, cruise missiles, third generation MBTs like the T-90S, M1A2-SEP, Challenger-2 etc, APCs & IFVs such as the BMP-2, Warrior, M2A3, Howitzers like the M109, MLRS, and toys like thermobaric weapons, clashing not just in Ukraine but in the Baltic States and the Baltic Approaches, Belarus/Poland (depending on the course of the war), the Atlantic, the Black Sea & the Med and possibly in the Pacific. And the fighting wouldn't just be contained to the front lines. In any serious conflict Russia would strike NATO harbours & airfields in the UK, Low Countries, Germany etc and NATO would be hitting Russian road and railway nodes on Russian soil.

You're looking at 100,000 + dead on NATO's side, with countless Russian casualties. Civilian casualties would be higher than anyone would like to think about. That's assuming the nuclear genie remains in the bottle.

However, Moscow was definitively prepared to utilize Russia's nuclear arsenal if NATO attempted to interfere in the annexation of Crimea. Should NATO have decided to act more strongly, with advisors and weapons being sent to Ukraine, ships in the Black Sea, CAPs on behalf of the Ukrainian Air Force, amongst other measures, things have a very small, but very real, potential to spiral out of control after a series of miscalculations or mishaps. The only way a war happens if both sides react strongly to provocations by the other, and this leading to a shooting war; NATO deliberately going to war with Russia is not realistic; blundering into conflict is far more likely.
 
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