Here’s what I did. While it’s pretty much inconceivable all neutral countries would go to war if one of them was invaded, it’s NOT inconceivable some would have alliances, regional in nature and among countries with shared interests. Excluding Mongolia (whose rules I left the same), I created 4 alliances among the remaining neutrals. No, not everything in these alliances make sense (Switzerland and Afghanistan would never go to war unless they were invaded), but it adds a new dimension to the game. Also, invaded neutral countries have an impact on geopolitics, so countries need to think carefully before attacking. It is risky and costly, however, in some cases there is value in doing it - unlike in the actual game.
Here’s the way it works: each alliance has one country that is the center of it all. This is the real gem - it either has the most IPC value or strategic value. The four countries are Sweden, Turkey, Argentina, and Spain. These countries each have a minor IPC and a proper military. This was easy to pick out, as these countries all had at least 2IPCs in value and 4+ call-ups. So I took their initial call-ups, and added 40IPCs worth of soldiers/bases for Argentina (4), 50 to Sweden and Spain (6), and 60 to Turkey (8). I based the units on what such a country would reasonably have. Sweden had advanced industry and an effective navy but hardly any air force in 1940; Spain was along the lines of Italy in land power, Turkey was mostly struggling to modernize but had fortifications and a small but professional british-trained air force (insignificant navy), Argentina had a small army and navy (though far better than its neighbors) and a great port.
Here are the official rules and set up:
If you attack a single neutral country, not all of them will become hostile - only ones they have a mutual defense pact with. There are four alliances on the map; an attack against one of these members is an attack on all.
Mongolia is unaffected by these changes.
If a territory/alliance is attacked, it will immediately join a specified member of the opposite side.
Note: Each South American neutral “country” for our purposes has been combined. For example, Venezuela is now a part of Ecuador and Colombia. “Greater Venezuela” does not receive an IPC bonus for this, however it does receive an additional infantry unit per added territory. So instead of spawning +2 infantry when attacked, it will create +4. Same rules apply for Greater Argentina (Argentina/Uruguay/Paraguay) and Greater Chile (Chile, Bolivia, Peru).
Finally, note that Sierra Leone is UK territory and Liberia becomes a US territory once it enters the war. They are not neutral territories.
Starting Neutral Territory Units:
South American Alliance:
Greater Venezuela: 4 Infantry
Greater Chile: 4 Infantry
Greater Argentina: 6 Infantry + 3 Artillery + 1 AAA + Naval Base + Destroyer (Sea Zone 85) + Minor IPC
If attacked by the Allies, the South American Alliance joins Germany. If attacked by the Axis, the South American Alliance joins the US. All of the South American Alliance’s units and factories immediately become controlled by that player. An Axis attack on the South American Alliance is considered a declaration of war against the US. The US may not attack the South American Alliance until war against Axis has been declared.
Total Alliance IPC Value: 6
Spain: 8 Infantry + 3 Artillery + 2 Tanks + 2 AAA + 1 Fighter + Minor IPC
Portugal: 2 Infantry
Mozambique: 2 Infantry
Angola: 2 Infantry
Rio de Oro
If attacked by the Allies, the Iberian Alliance joins Germany or Italy. If attacked by the Axis, the Iberian Alliance joins the UK (European Economy) or France. All of its units and factories immediately become controlled by that player. An Axis attack against Spain is considered a declaration of war against the US.
Total Alliance IPC Value: 5
Sweden: 6 Infantry + 4 Artillery + 2 Tanks + 1 Mech Infantry + 2 AAA + Destroyer (Sea Zone 113) + Minor IPC
Switzerland: 2 Infantry
If attacked by the Allies, Sweden joins Germany and Switzerland joins Germany or Italy. If attacked by the Axis, Sweden joins the UK (European Economy) and Switzerland joins France. All of their units and factories immediately become controlled by those players. An Axis attack against Sweden or Switzerland is considered a declaration of War against Russia and the US.
Total IPC Value: 3
Turkey: 9 Infantry + 4 Artillery + 1 Tank + 1 Fighter + 2 AAA + Fortification + Minor IPC
Saudi Arabia: 2 Infantry
Afghanistan: 4 Infantry
If attacked by the Allies, Turkey and Saudi Arabia join Germany or Italy, and Afghanistan joins Germany. If attacked by the Axis, Turkey and Afghanistan join Russia or UK (European Economy), and Saudi Arabia joins the UK (European Economy). All of the Islamic Alliance’s units and factories immediately become controlled by that player. An Axis attack on the Islamic Alliance is the equivalent of a declaration of war on Russia, the UK, ANZAC, and France. Russia may not attack the Islamic Alliance until war against Germany has been declared.
Additionally, the Bosporus Straight is considered a universal national objective worth an additional +1 IPC to the player controlling it.
Note: Italian and German national objectives include Saudi Arabia in their quest for Strategic Oil Reserves. If controlled, they gain an additional +2 IPCs such as in Northwest Persia, Iraq, and Persia.
Total Alliance IPC Value: 5