Very interesting question regarding the third world war. The fact is that if you look at all the military conflicts that are happening now and then Who is involved in them, clearly one can come to the conclusion that all these wars will not end so quickly yet. If you pay attention to Syria and even to North Korea, you can definitely say which countries will be the culprits of the 3rd World War
North Korea is not going to attack anyone. Their's is just empty talk. Let's focus our attention on Syria. It is true that most of the world powers are involved in Syria. But their involvement is limited to air-strikes and training. So the Syrian conflict also is not going to escalate in to a world war.
This is incorrect. Syria is already a world war. The price of oil is low and likely to decline further. Russia is not interested in a stable situation in Syria. This can significantly reduce the volume of sales of Russian hydrocarbons to Europe. So they will do everything so that the world did not come in Syria.
Sithara is referring to world war as in all encompassing global conflict - in response to the OP
world had not seen such war since 1945. In this matter Syria is just another battleground where powers - both global and regional, settle their differences.
I am glad, that North Korea ended up to be what I guessed in the first place, foreign policy recon.
If a single country used nukes at the start of a great war, everyone who has access to nukes would follow suit. Though i don't think england would be the first one to do this and hopefully no country would be stupid enough to initiate a nuclear attack. A nuclear warfare would mean almost extinction level disaster for everyone.
I guess the most powerful nuclear weapons have a blast radius of less than 100km. So a nuclear warfare doesn't automatically mean the end of all forms of life on this planet, at least for the short term. But in the long term, survival will be difficult, provided how quickly the radiation spreads through air and water.
This is only a theory. The Japanese survived after the nuclear bombings, and Chernobyl disaster. There are many people who never left the area of infection and safely live there still. Animals are also great feeling in there. The effect of radiation is still too poorly understood to speak of the destruction on the planet.
It is not theory. Nuclear fallout is well documented. Bombs dropped on Japan were very inefficient by modern standarts, yet both managed to wipe in excess of 70 000 people on impact, killing about as many in fallout and related diseases. That was well before "dirt" bombs were developed.
Majority of fallout diminishes within first six months, but you are forgetting, that its particles stay in objects such as trees, buildings, even ground - in essense making the are infertile. Enough bombs would cause nuclear winter. Small amount would still kill majority of population as infrastructure, agriculture and health care would collapse.