The world war three scenario is appropriate given that the Doomsday clock is now at its closest point to midnight in thirty years
Obvious problems are:
1. In 1939 there was no superpower. In 1939 the USA had pursued a policy of isolationism and almost pacifism. The army was run down and the navy was only one of the world's navies. Today the USA is the world's only superpower. It's military spending is greater than all its main enemies and allies combined. Effectively nobody can fight the United States of America. However the United States of America has potentially more to lose than other nations and whether it would be prepared to go all in on a bet on say Turkey or Saudi Arabia (given both nations assist ISIS) is questionable.
2. In 1939 the world's population was one billion and life was short. In 2012 it hit seven billion. by 2026 it will be eight. Not only is the population increasing but life expectancy has increased rapidly all over the world. In 1950 the world average was 48. Today it is 67, and much higher in developed nations. In 1939 developed nations meant white nations plus Japan. Now it means North Asia, South East Asia, Europe and North America. So called second world nations like Egypt, Kenya have very high life expectancies. In short where before life was more intense, far riskier and more of a gamble today it is a more kinder and more leisurely stroll with more risk from traffic accidents than war, starvation or most diseases. The whole world has become more civilised.
3. In 1939 US national debt was around 50% of GDP it peaked at around 120% at the height of World War Two. Right now it's 106%. The US "war on terror" has killed up to 86,000 non US enemy fighters, 151,000 Iraqi civilians, 19,000 Afghani civilians, and 2,300 Pakistani civilians, for the loss of 6,600 US military killed and 3,000 plus civilians killed (9/11) for a total cost of US$5,000,000,000,000. New Zealand's national debt is around 30% of GDP. Australia's 33%. Most of the Euro zone is around 90%. In short another war could do colossal damage to the West's economy.
4. In 1939 there were no long range ballistic missiles. The Germans developed them in 1942. The long range ballistic missile means that war can now begin (and almost end) in a matter of hours. Nations with ballistic missiles include: US, Russia, China, India, Britain (Trident submarines), France (Redoubtable submarines), Israel, South Africa, Pakistan, Iran, North Korea. Nations which could rapidly employ ballistic missiles include Japan, Germany, and, weirdly enough, New Zealand. The logic of war with ballistic missiles is to target the enemy missiles and try and end up with the only ones left. Submarine launched missiles make that difficult. Russia has recently discussed a strategy of first use as a means of deterrent. Instead of targeting enemy missiles Russia would target enemy cities. This would assure mutual destruction but it assumes a US president would blink first. Obviously you can't play Russian roulette too often without losing badly.
5. In 1939 the only weapon of mass destruction was toxic gas which required a fleet of unopposed bombers to deliver it. Aside from a few incidents and accidents gas was not used in warfare in WW2 (although it was used in genocide). Today weapons of mass destruction include plutonium thermonuclear weapons, uranium fission weapons and dirty bombs, and potentially most destructive of all, biological weapons including weaponised anthrax, ebola, plague, etc. Toxic gases are more powerful than ever but are not normally deployed on ballistic missiles. Nuclear states are mostly those with ballistic missiles except Iran. Japan and Germany could probably become nuclear states in about five minutes. Sweden, Korea and Australia would take a bit longer. South Africa's nuclear status is doubtful.
6. In 1939 there were few networks. Today most of the world's work is done on computer networks and the internet is already regarded as a battlefield of enormous importance. In 1939 most corporations were populated by a single nationality. Today most corporations are cultural melting pots of numerous nationalities. People in 1939 rarely knew anyone from another nation. Today the internet and social media makes connection with people from other nations simple. When Israel recently attacked Gaza it took a storm of protest and negative publicity on social media and despite social media brigades clearly lost a lot of support.
7. In 1939 illegal crime was small beer. The nearest crime got to major league was the Chicago mafia which grew during the prohibition (1920-33) but that was relatively small. Today's drug, arms and human trafficking markets are enormous often eclipsing the power of the states they originate from. Moreover institutions such as multinational banks, intelligence agencies, and governments have become complicit in the operation of these black markets. Today ISIS and the Taliban relies on Turkish oil and drug smugglers (respectively) for its economic survival - a fact the Russians have made embarrassingly obvious. Turkish drug and human smugglers are also effectively holding Europe to ransom and there is good evidence the Turkish state is complicit. The same is also true in Latin America where the economic power of cartels effectively makes them major corporations.
8. In 1939 war made sense economically. As the famous anthropologist Jacob Bronowski observed 'war is organised theft'. Britain had stolen India, Persia, Arabia, Egypt, and much of Africa. France had stolen nations as well as had much of Europe. The Germans sought an "Anschluss" to reform an economic unit which had been wrecked by post WW1 border changes. Austria, the Sudetenland, the parts of Czechoslovakia, and parts of Poland, were all parts of the former German economic entity. Divvying Poland with Russia made sense to both dictators neither of whom liked the Poles or trusted each other. In Japan's case its adventure in China was replacing native Chinese warlords with harsher Japanese ones, but nobody was particularly nice. Japan's only problem was that Roosevelt cut off her oil and her efforts to get oil from Siberia were flattened by Marshal Zhukov. That almost forced Japan to attack the Dutch East Indies where Mobil had its refinery. Today economic advantage comes from intellectual property - knowledge. Nations that don't trade and become militant (e.g. Iran, Cuba, and North Korea) get cut off and suffer economically.
1. Invasion is unlikely. Only if the north were uninhabitable would anyone bother to come. If, in the extremely unlikely event the US was destroyed and China became the predominant power, it would be very weak and simply seek to re-establish trade on favourable terms. Peaceful invasion is much cheaper than military invasion for everyone. If the north was uninhabitable it would be pointless because it would probably mean the planet's ecosphere was dying and life on earth was over.
2. World war three is likely to start with a flashpoint and stop with a political settlement. Likely flashpoints are Syria/Iraq; North Korea/Japan; China/Taiwan-US;
3. World war three's actual start can only be defined as being when a major military power goes "all in" to achieve a political objective. This will be preceded by a long period of instability and confusion.
4. World war three will be multi dimensional involving huge capital movements and cyber attacks. Unofficial Chinese policy is total war involves all possible dimensions of conflict to achieve
1. Extremely good cyber defence would be the first and most important area where the protection of the country would be important. Knocking out or infiltrating New Zealand networks could provide attackers with information or cover for attacks on other nations.
2. It is unlikely that anyone would attack us with ballistic missiles as we present no threat and ballistic missiles are best employed on targets that constitute a threat. There are very few ballistic missile defence systems in the world outside the US, Russia and Israel.
3. There is almost no likelihood of any need to send our military anywhere given that it would always be 1) too small to be of any consequence and 2) politically irrelevant given the scale of the conflict.
4. The real question would be what sort of military would we need in a post WW3 world? But that is unknowable at the present time.