Depends what you regard as 'the height', but regardless, the post-war situation is going to be colossally different.
I'd say it would suck to be the soviet union.
I would have to agree; telling someone to just use the Search function is a fine response when it's a topic that has been done to death, but when it's just something that's come up a couple times over the many years AH.com has been around there's no reason there can't be a new thread to discuss the matter.
Yellowstone erupting means that the US stays out of World War II in any significant way. Considering the fact that everything west of the Rockies is going to be devastated, the US would need years (maybe even decades) to fully rebuild its power-projection capabilities in the Pacific. Isolationism would dominate the political scene, since everyone would care far more about rebuilding than wars in Europe and Asia. The embargo against Japan doesn't come up/gets dropped (depending on when in 1941 the eruption happens) since the US needs all the trade it can get for rebuilding funds. Lend-Lease goes away, although the US probably retains cash-and-carry; every bit of trade they can get will help.
If the eruption happens after Pearl Harbor, the US would basically have to concede its Pacific holdings to Japan; with the entire West Coast smashed to bits operating any significant military force in the Pacific would be impossible. The US would probably have to settle for sending expeditionary forces to Australia and New Zealand and relying on the allies to keep them supplied. Europe probably only gets a token force, since a major military deployment when the homeland is in ruins would be politically impossible.
To stay away from the asb discussion, i do think whenever Yellowstone supervulcano erupts, it will be a BIG eruption. Just due the size of its caldera.
Will it be an extinction event, not likely, far more population then during Toba.
Both the Toba explosion and the last Yellowstone were VEI 8 eruptions (1000m3). And Toba definately brought mankind close to beingh extinct.
Even if the eruption would just be a VEI7 the direct result would be a huge volcanic winter.
When it takes place in autumn/winter the effects might be slightly less due to the fact that all harvesting has already been done.
But when it takes place earlier in the year, expect widescale famine.
Will the US/Canada survive? in case of a VEI7 yes, although will lose quite some population.
In case of a VEI8: Not in a way that you will be able to recognize.
Result of VEi7: war effort will probably collapse, fight for survival will prevail, although society will most likely not collapse. Russia will get rather frigid for a while. Famine
Result of VEI8: Total collapse of society, chaos, return to the dark ages or something like it. Catastrophic famine. Large portion of human population will perish.
The US is set back decades for recovery, the West Coast will become inhabitable... after a few decades, inevitably someone will want resources and new, fertile land might emerge from the devastation.
Worldwide colder temperatures mean diebacks worldwide, of both humans and nature. Survivable but shitty conditions worldwide. USA will be hampered as a world power and it probably won't truly emerge as a superpower until way later.
No WWII though, even psychotics like Hitler won't last long trying to make war in what will seem like the apocalypse to many.
Main effect besides the actual eruption and such? Global crop failures form a lowering of temperatures.
In WWII the global temp rose by a degree or so due to the war, expect it to now be -4 below average or so for a few years.
That would cause famines.
Russia would fall, and germany would severely stall.
WWII ends in a few years later with the US using nukes on cities such as Dresden, Berlin, and various Japanese cities. So with much more damage to everyone. This assumes the 1941 eruption is post december 11th. I seriously expect tidal waves to strike the east pacific off and on for months/years. This seriously screws over Japan, and it would probably slow their stomp across china, and their moves towards US assets and Australia.
There is a chance the eruption can trigger sympathetic tectonic activty across the globe, i.e. Earthquakes/tidal waves etc..
And thats only with a VEI7 eruption.
How did you get the idea of nukes? the original poster said 1941. So if it happens early enough in the year, no pacific war simply because I would doubt if the oil embargo against japan would hold up thus no war, and also don't even think anyone would even bother at this point to continue the war under the given circumstances And don't forget the us would have lots of other things to to pay than developing nukes. Just the suggestion of developing nukes in a situation like this would be the fastest way for a pres to get himself removed.
As for europe, 1941 & 1942 otl were already heavy winters, add this and you have the winters from hell. No lendlease or external supplies due circumstances and to murmansk most likely being frozen shut and russia will have major famine.
Unfortunately the nazibunch might see this eruption as an act of god.
But nevertheless the war would be over rather soon.
As to a VEI8 - exit civilisation and most likely a large part of mankind, plus a new ice age.
Have concur with the others an eruption at this point even a VEI7 would mean the end of the war.
I'd say it would suck to be the soviet union.
The Wehrmacht's infantry divisions can ice skate across the Channel in the final phase of Operation Sealion.
Only to find that the British had went around them and launched an attack into France.
Cooler climes, does that mean that formerly hot-desert countries like Australia could become grain producers?
The Wehrmacht's infantry divisions can ice skate across the Channel in the final phase of Operation Sealion.