How real is a nuclear war.

It hasn't happened yet.

My guess is not very likely unless forces cross into Russian territory. There are a number of countries that are friendly to Russia (China) or neutral to friendly (India, Saudi Arabia, lots of Africa). No one is going to be friendly to Russia if they start dropping nuclear weapons on Ukraine. I'm not all that sure the Russian public or military would support that either. Nuclear fallout would tend to move from Ukraine towards Russia and there is no way to keep secret that a "special operation" that "is going well and meeting all objectives" required nuclear weapons.

No sane person would use a nuclear weapon unless it were absolutely necessary as a last ditch effort to defend one's country. Let's hope Putin is sane.

See Zechariah 14. The day when the LORD will sit in judgement is near. Then Jerusalem will be looted, and the loot will be divided up before your eyes. 2The LORD will bring all the nations together to make war on Jerusalem. The city will be taken, the houses looted, and the women raped. Half the people will go into exile, but the rest of them will not be taken away from the city.

Then the Lord will go out and fight the enemies of Israel; those Nations who surround Jerusalem in their attempt to drive God's chosen people into the sea.

The African tectonic plate in its northern migration, grinds against the Arabian plate in a line that runs up through the Red Sea and along the Jordon valley beneath the Mount of Olives.

Zechariah 14: 3-4; Then the Lord will go out and fight for his people as he has fought in times past. At that time, he will stand on the Mount of Olives, to the east of Jerusalem. Then the Mount of Olives will be split in two, from east to west by a large valley. Half of the mountain (On the African plate) will move to the northwest, and half of it (On the Arabian plate) will move to the southeast.

Could the violent activity around the earth at this time, be the trigger that will cause the super volcano beneath Yellow Stone to erupt, enveloping the planet in a cloud of debris?

14:6; On that day shall be neither cold nor frost, nor day or night, but a perpetual twilight.

Zechariah 14: 13; Then the Lord will throw those nations that surround Jerusalem, into a state of total confusion, and the weapons of destruction with which they would destroy Israel, he will cause them to turn upon their own allies and they shall suffer a terrible disease, the soft tissue such as their eyes and tongues will melt in their sockets, and their radiated flesh, cooked to the bone, will slide from their bodies while still standing. Then all the surviving Nations will send their representatives each year to Jerusalem in the land of Israel, to worship and pay tribute to the Lord who will rule the whole world with justice for a thousand years, and woe betide those who refuse to do so.

Then all the godless people of this world, and all those, who in their Synagogues, Mosques, and Cathedrals of stone, marble, or crystal, who prostate themselves on the floors or who sing and dance with their eyes and hands raised to the heavens in worship of a god they neither know or understand, will bow down and worship THE MOST HIGH of the Bible.

In dream I saw the heavens ablaze with balls of fire
Huge hailstones that were burning and streaking down the skies
The earth was clothed in purples, dark orange, and deep blue
Like a swaddling cloth surrounding us that hid the stars from view
Dark clouds rose from the mountain peaks, earth's veins were opened wide
Through which her inner blood spewed forth in streams of living fire
Whole continents, they heaved and tossed, waves rippled through the ground
In all the earth, no hiding place of safety could be found
The oceans boiled, they foamed and rose destroying cities on their shores
All the river dams were busted, valley towns were seen no more
The power stations of the earth--all were melted down
A few survivors of the human race were all that could be found
And then I saw the winter, a winter so severe
It lasted not a few short months, but many, many, years
And the women who were pregnant, Ahh, the children that they bore
Grotesque and hideous malformations, I pray to see that sight no more
Then when the winter lifted and the crops began to grow
A strange and eerie world emerged from the destruction and the snow
A world with neither day nor night where rainbows couldn't form
In the atmosphere above the earth, and yet the air was strangely warm
A thousand years of twilight and through that swaddling band on high
Three blood red giants were blazing through a hazed and orange sky
The sun and moon had turned to blood, but far brighter than the moon
Was Jupiter, that heavenly light, which in time would spell man's doom. . . . . The Anointed.

I see many quotations in your response. What makes you think that the source is correct or reliable?

Everybody thinks (or hopes) it is unlikely, until it happens.
In the long run, it is probably highly likely that nuclear weapons will be used by someone, somewhere, sometime. And at the rate that proliferation is proceeding (North Korea, India, Pakistan) and the increased development of delivery technology (hypersonic missiles) it's probably a good guess that it will happen in the next five years. Whether or not that leads to all-out nuclear war is a more complicated question, but I wouldn't rule it out.