OK, I disagree with the folks here who say this map is a little tough. It's REALLY tough. :-) Took me at least a dozen tries to beat it. The strategy I came up with in the end is what I call: *puts on best Futurama comedy voice* CHANGE PLACES!!!
There are 3 AIs; I'll call them the Swedish AI, the Italian AI, and the Parthian AI.
The fundamental difficulty is that the Parthian AI has a huge advantage in its starting position. You'd like that starting position, wouldn't you? Then you could win easily. Well, let's change places with the Parthian AI; he can have the UK, we can have Partha. Then we'll see who wins...
First, take the UK as quickly as possible. Then hop along to Denmark with your commander and take out the Swedish AI (this should be easy - move your commander and no armies next to the commander, put 4 armies on and attack. The AI will always lose.)
Unfortunately, to win this map there are a couple of things that have to go your way based on pure luck.
Aggressively expand down into France and Spain. This is one part where you need to get lucky; the Italian AI boss needs to come up into France or Spain. If he comes up into Germany I'd just start over. Dealing with him, as others have said, involves surrounding him with 3-army stacks and taking his square at the end of each turn with several of them. The other part where you need to get lucky is that the Italian AI needs to not put up too much resistance when you expand into France and Spain. You need to capture them very quickly to get enough armies; if the AI throws a spanner in the works too often, give up and try again.
On your eastern expansion wing, be building up a mega-stack each turn. By the time you hit the Parthian AI it should have 80+ armies, and you should be getting about 100 armies per turn. Pierce through the Parthian AI front line tidal wave with this stack, and keep your commander in the stack. He needs to move into Turkey along with it.
Once your stack is in Turkey, fan out and start gobbling up the Parthian AI's territory, and ignore your territory to the west. Focus 100% on expanding to the east. The Parthian AI won't put up much resistance. What we're doing is changing places with the Parthian AI, because trying to deal with its several mega-stacks head-on is pretty much impossible. You're knocking out its bonuses such as Magna Asia, Partha, and Parthian Empire, and getting that nice eastern territory for yourself. The Parthian AI's mega-stacks will keep pushing west, allowing you to be free of them when taking its eastern territory.
By now you're expanding heavily into the Parthian AI's territory and your commander is in the east, so even if the AI manages to take all your territory in the west your commander is OK. As soon as possible, start pushing back to the west as well. To the south-east, build up two mega-stacks and once they're nice and big (like 100 each), send them to Persepolis in a pincer movement. The Parthian AI will try to place all its armies on the commander's tile but your stacks should be too big for it to defend against. With the Parthian AI killed, mopping up the remaining neutral territories to the west and finishing off the Italian AI boss might be slow, but it's straightforward.
This tactic aint the fastest but it's the only one that worked for me!
Here's a summary image of how I did it: https://i.sli.mg/VzjmTY.gif
I also made it into a YouTube video: https://www.youtube.com/watch?v=hp_yln2mQNY
Edited 12/6/2016 11:42:49