I have found that it is fairly easy to get Japanese units to the Russian’s doorstep via Persia. What is more difficult to do is to get enough units there to be a real threat. Between attrition, taking territories to build income, and watching your back for the US, Japan can get spread real thin despite having perhaps the highest income of all the players.
Depending on how hard the UK fights, Japan can be in Persia on J2 if they want and have an Indian IC building tanks on J3. Unfortunately, Persia can quickly become a dead zone until Japan has enough force to hold it. And just because they can hold PER doesn’t mean they can take CAU right away. A lot depends on how effective Germany has been on their side of the front. Unless they are very lucky, I don’t think Japan can assemble a worthy attack force in PER until at least J7, and that is a long time in this game particularly if the US is making threatening moves on the Japanese territories in the Pacific.
Don’t get me wrong, I think BUR-IND-PER is a great way to go. But Russia needs to be pressured on multiple sides. Maybe some Japanese units coming through China (MAN or JAP IC builds), some coming from the south (IND, BUR, FIC, or SUM builds), plus some German pressure from the West. Otherwise, Russia can easily hold off any one of these fronts for quite a while.
So far, I am finding AA50 to be a very fluid game. What works in one match, may not work in another. A lot depends on the decisions made by your opponent, and how you respond to those countermoves.
There is a oft-repeated piece of military wisdom (variously ascribed to either Clausewitz or von Moltke) that goes, “No battle plan survives first contact with the enemy.” Make all the plans you want, but be ready to throw the original plan away the moment it is no longer working for you.