Albert Einstein once said that he had no idea what kind of weapons would be involved in WWIII. However, he was certain that WWIV would be fought with sticks and stones.
There are many signs that WWIII is nearly upon us. ISIS, Russian aggression, Chinese aggression, Iran nearing nuclear weapons, North Korean aggression, and United States debt and eventual economic collapse.
As a US citizen I've watched the population of my country become a very complacent people. Having never seen war on our soil and very distant from the great depression, the current generation does not understand the dangers lurking in the weeds. Unfortunately, we are nearing a dramatic wake up call in the near future.
Throughout history, civilizations have risen and fallen. The Dark Ages were not considered to be an apocalypse, although the one you suggest is impending would not be so different. Even if war were to break out on a sufficient scale to destroy most of civilization, it would still survive along with technology in small pockets, and as long as nuclear weapons were not used in excess, these pockets would quickly expand to form new civilizations. The use of nuclear weapons would not benefit anyone, and since the US has superior nuclear capabilities, any other nuclear powers would have a severe disadvantage in a nuclear war, and would consequently be reluctant to use nuclear weapons. Russian aggression and suboptimal relations between the US and China are nothing new. The Cold War was ended without WWIII breaking out, and relations between the US, China, and Russia were far more strained during that period. China depends on the US consumer market for economic growth and stability, and this would be more than sufficient incentive not to engage in any direct military conflict with the United States. Russia's economy and population are shrinking, and their ability to do any damage is becoming increasingly limited. Conditions today are far less conducive to WWIII than they were during the Cold War, and since there was no global destruction then, it wouldn't be rational to assume we are approaching such an event now.
The United States is in debt and has a weak president that has made every effort to solidify and expound upon that debt. Most of that debt is owed to China. Although the Chinese presently depend upon US economy to sustain their economy, the US is so indebted to them that they actually consider the land theirs at this point. With the growing differential in male to female ratio resulting from population issues in the country hormone levels are affecting their judgement when it comes to a standoff where war is concerned. Who is to say the "apocalyptic" devastation will be nuclear. A nuclear war would destroy the land they believe they already own due to the debt that is owed. What better way to collect their land than an EMP? And, that is just China and US we are talking about.
China and Russia are already the key players in collaborating replacing the US dollar for oil trade. Saudi Arabia is the country that has been the strength toward continuing to hold the US dollar as the standard toward oil trading. However, the US submission and appeasement of Saudi Arabia's greatest threat (Iran) has weakened that strength. The fall of the US dollar in oil trading will send the United States economy into an unrecoverable economic spiral.
Take the above and add ISIS, Israel, Europe (Economy), North Korea, Japan, and the Middle East as a whole ... The writing is on the wall. You (and Einstein) are correct in that the apocalypse (WWIII) may not be in totality, but it is inevitable and it is near. The world will never be the same after. And the complacent USA isn't nearly what it was when WWII occurred. The US is a divided nation of selfish entitled vs. selfish entitled.
The reason the apocalyptic devastation would need to be nuclear is because this would be by far the most likely type of destruction to cause mass global destruction due to the lasting pollution it leaves behind. This pollution would ensure the inability of civilizations to rebuild quickly enough to avoid being destroyed. An EMP would indeed be much more sensible for China to use, but the US coming under Chinese control would not be considered mass global destruction. The argument that the US is facing economic collapse is a digression from the main argument, and besides that, oil is not a sustainable source of energy, and the current president has helped the US become a leader in renewable energy. Middle Eastern instability is nothing new, there is no reason to believe Israel will bring about an apocalypse, Europe's economy has suffered before, and it was much worse in the years leading up to WWII. As for Japan, it has a shrinking population and some economic issues but that is irrelevant to the debate. Even if Iran develops nuclear capabilities, the more advanced nuclear nations already have interception systems. This debate is not on whether WWIII will occur, it is on whether it will cause global devastation. ISIS is probably the most plausible threat to civilization because they really may seek to bring humanity back to the year 1000, but so have other radical Islamist groups, and they all failed. There is nothing that makes ISIS special. Even with the destructive power of modern day technology, global destruction is highly unlikely because it goes against the interests of the nations most capable of causing it. An apocalypse is more avoidable now than ever due to the lessons learned from the past. Nothing happening in the world currently makes it more likely now than ever before. Consequently, there is no reason to believe we are nearing such an event.