Playing Persia[edit]
Persia is amongst the most minor category of nations in Hearts of Iron III, with a Base Industrial Capacity (IC) of just 5. On the face of it, a country this minor does not have much going for it. They're sandwiched between Afghanistan; a nation with about 2 Base IC, Turkey; a nation starting at about 25 Base IC, who can easily flatten them, the remainder of their border is either UK colonial territory (India) or UK Puppets (Iraq); aggravating these regions is something you'll want to only do with a lot of preparation, to the North is the Soviet Union; they'll crush you the minute you try to move against them at any point directly. At this point, a lot of players would simply pick a different country.
It may come as some surprise that you can, therefore, change the outcome of the war entirely and win the game with Persia. They hold a lot of the worlds oil production, and with that; the key to deciding who wins the war, and therefore who you want to ultimately side with. Oil in Hearts of Iron III (HoI3) means Fuel, and Fuel means your Aircraft can fly, your ships move above 1kph and your vehicles (mostly Tanks, in the case of the Major Powers), can attack whatsoever and also fight at full effectiveness. Even an army with no vehicles and therefore no Fuel requirements whatsoever will suffer a drain on manpower, and eventually not be able to replace losses or build anything new. This makes controlling the Oil in HoI3 absolutely like being the kingmaker; just as long as you can hold on to it and minimise what other nations produce.