The trigger for WWI was the assassination of Archduke Franz Ferdinand of Austria by Yugoslav nationalist Gavrilo Princip in Sarajevo on 28 June 1914. Germany presented an ultimatum to Russia to demobilize, and when this was refused, declared war on Russia on 1 August.
The immediate cause of World War 2 was the German invasion of Poland on 1 September.
I think that mankind is now mature enough to not take such a step anymore and destroy life on earth. But, to be more conservative, I would say, if it is to occur, it will not be in the same manner as World War I and World War II.
It may involve evacuation of small poor parts of the world from inhabitants, to enable the relocation of others, and the use of resources in evacuated land, in favor of the invaders.
Wars may occur, when the balance of power is perceived, by each party, to be in disequilibrium, in his favor.
Now, who will participate in such war, on top? Let aside small allies.
We can name Russia, Iran, China, USA, North Korea and Israel as candidates for a confrontation. Probably each of them believes he is capable of achieving victory and imposing superiority.
Next question is, where could the war start?
All candidates are mature enough not to be part of a Global war with hot spots close to their borders. They will try to create hot spots close to the other party borders. Regional wars to be ignited, that involve the participation of the other party, and aim at exhausting his abilities, before assumed confrontation. Same game previously played by the USA with Saddam Hussein, by supporting his war with Iran, followed by encouraging his invasion of Kuwait. The game ended up by exhausting his military power and facilitated the invasion of the USA to Iraq.
What is going on in Syria, is far from the borders of all candidates except one which is Israel.
Israel, EU, and the USA stand on one side, and I shall refer to as Western Camp. On the other side could be Russia, Iran, China, and North Korea, referred to as Eastern Camp. Clearly, the Eastern Camp has a more in terms of geographical, and demographical power as well as competent economic and military capabilities.
The current allies will not remain so, for long. It is just a temporary relation, within a long strategy. However, for now, the balance of power seems to be in equilibrium. Attempts are made, though, to shake it violently.
Interference by Nato in Lybia, by Saudi in Yemen, by the USA in Iraq, as well as the introduction of ISIS in the Middle East, suggests that the Western Camp has been dragged, strategically, to artificial hot spots, in order to exhaust their military abilities. Also, it seems, that exhausting Saudi Arabia financial abilities, by its paying the bills.
Israel has built up an economic empire, with huge financial influence all over the world. Its secret intelligence agency (MOSSAD) has enlisted local VIP's to serve its agenda, including Presidents, kings, military officers and secret intelligence people in other countries. Isn' that enough to ensure their safe existence that was threatened in the past by Hitler, and not too far by some Arab Countries (became neutralized later), and lately by Iran.? In addition to the claim of seeking security, there is, also, their ambition of extension beyond borders, and ruling the world as explicit Super Power, in accordance with their religious beliefs.
Saudi Arabia, being Sunni, find themselves accused of supporting terrorism since ISIS and Taliban are also Sunni. (However, Taliban was - most likely supported by CIA - introduced in the scene to fight USSR, and It is highly suspected now that ISIS is supported by Russia and Iran, and was introduced in the scene to exhaust the Western Camp)
How could it be that ISIS, the Sunni, is owned by Iran? The simple answer, is, to remove any suspicion of being supported by Iran. ISIS was born to die, but before death, it has a mission to exhaust the Western Powers.
Despite its maturity, mankind is still under the threat of a crazy order, that might be given by a crazy politician, to ignite ww3.
What - do you think - could be the trigger for WW3?
- Assassination of Trump.
- Assassination of Putin.
- Assassination of Assad.
- Assassination of Bin Salman.
- Assassination of Khamenei.
- Assassination of Kim Jong-un
- Invasion of Qatar by Saudi Arabia.
- Invasion of Syria by Israel, in response to Iranian threats.
- Collapse of Ethiopian Dam, with accusations pointing to Egypt.
- Others