Hi, I'm new here (and to the Total Diplomacy website, actually), but I've been playing Risk for nearly 5 years, so I've learned a thing or two. Also, I know I'm pretty late (it's been a year later since the previous comment), but like I said, I'm new to Total Diplomacy.
As to this scenario, it truly depends on the card value. For example, I see that only one color (yellow) has the potential to turn in cards by the time the round gets to blue. Assuming yellow can turn in the cards, he will do so in order to take out black in North America as well as the threat in Kamchatka. He will attack the latter territory at all costs because black might turn in cards when his turn rolls around and if he sees the fight in Australia heating up, he might call it quits in Australia and turn to his somewhat well-fortified territory Kamchatka and quickly sweep North America. As a result, yellow will try to take black in Alaska and Kamchatka.
Of course, there's always the chance that yellow can't turn in his cards. If that's the case, he needs to be ready to take a hit because black is almost guaranteed at least 10 more troops plus his regular 3. He might receive at least 13 troops. Chances are, black will place those troops in Kamchatka and attack east into Alaska, threatening yellow harshly.
With regards to blue, considering I won't be able to turn in cards, so no reinforcement bonus comes to me. Looking east is hotbed Australia, but it's best to stay out of that fight. Asia is also to the east, but any player in his right mind won't let any other player conquer Asia. Africa can be for the taking, but like I said earlier, the cards come into play. Green is forced to turn in his cards. Depending on yellow, he will receive his 8 or 10 troop bonus plus his 3, giving him at least 11 troops. He will use those troops to take back his lost African nation and severely punish blue for his attack. To avoid this, I would move into Europe. Since I am lucky enough to go before green, I'd strike a deal with green, claiming that he should stay away from Europe if I don't attack his territories in Africa. Green will probably accept this for two reasons: 1. he wants to keep Africa and 2. he has another way out (South America). Green can do some damage in South America with his reinforcements. Of course, brown could always attack green in North Africa, but if he does so, there's an even greater incentive for green to accept my non-aggression pact.
So, let's say that green accepts that pact and, like, Grant Blackburn said, red does take Scandinavia for his card. Assuming red put most of his forces in Australia, considering he has most of his troops there, his troops in Europe will be a low number. For example, knowing Risk players, if they want a territory so much, they'll do anything they can to take/keep it. If red pours his reinforcements (3 rein.) into Great Britain, he'll attack Scandinavia and take it over. That's well and good, but he won't put all of his troops into Scandinavia; he will most likely split the troops into each territory. If he doesn't, he's making it easier for blue. However, blue goes much after red so red won't know what blue's strategy is.
Anyway, so blue makes that non-aggression pact with green. As a result, blue can start attacking in Europe. If all goes well, he will get most, if not all, of Europe. The "threat" in Greenland will most likely subside by the time yellow rolls around as black will most likely attack yellow in North America.
Now, there are some holes in my theory. First, let's say red decides to do some attacking in Australia other than Europe. Chances are, he will take either Eastern Australia (risky) or Western Australia (also risky, as that divides his troops). Either way, if red succeeds, he has no incentive to attack Scandinavia for a card. The 5 troops on Great Britain persist, but will continue to persist as long as red stays in Australia.
Black might decide that Australia is the way to go despite all the fighting and intensely fortify Siam (or Indonesia, assuming it's still under black's control). As a result, yellow might not have much incentive to attack Kamchatka, which could spell disaster for me. If I continue to attack Europe, my empire is pretty dilute by the time I arrive at Iceland. As a result, yellow might turn in his cards and get the 5 bonus from North American and eliminate me. Hopefully, yellow would attack South America, but if he goes for Europe, I will have to brace the attack and hopefully survive long enough to maybe cash in my cards the next turn.
I could also take over territories in Europe that do NOT belong to green. If I realize that I am not able to conquer all of Europe, I would attack all the non-green territories and ask green to move his troops out of Europe ASAP. If he does so, I will have eliminated the non-green threat in Europe and have green by a good as I won't attack him in Africa and he won't attack me in Europe.
This is my first solution idea, so I hope you all enjoy reading it. Also, I would appreciate it if you all tell me if there are any other holes in my theory. I haven't been playing too often, but I would like to hear your thoughts on this as well, Mr. Ehsan Honary As a Risk player, so many choices come to mind and a wrong turn could spell disaster.