I was playing a game of risk with my family, and it was put on hold in the middle of my phase of attack, therefore the ball is in my hands. I am the grey army. I believe if I attack the Red army in Alaska, I will win that battle. Because I would roll 3 dice against the smaller defensive force, who may only roll 2. I also tested it here: http://recreationalmath.com/Risk/ However, red can come back at me in the next turn, and flood its more concentrated troops into my empire, after shattering the attacking front. Therefore, I believe it would be more wise to hold off the attack, until I can also threaten Greenland; making it a two front war. I can hold off green in Africa, especially since Blue is threatening to them. Red and Green have promised not to attack one another for the time being. But that could be easily broken.