Anyone finish challenge 2? I can't make it to all the borders of my world before I'm invaded by 50+ armies of random colors. I did manage to abandon 20 armies just outside of my Argentina. That sufficiently closed off that access, which is the basis for my strategy so far. But I haven't been able to shut down more than 1, even if I make it to the border point before it's invaded. I also can't think of a place I can hole up and defend until I'm strong enough to mount an attack. Since it's 1 against 5, I can't imagine winning if I can't own my entire world before they break through.
The ones that have done it put their first abandon in Svalbard S. You can get to that by going south from your Africa starting place.Challenge 2 is hella hard. Some general tips I've discovered that apply to all levels:The AI values neutral territories much more than you do. What I mean by that is, if you are next to the AI, you are going to be focused on him. However, if there is a neutral adjacent to both of you, he will always attack that. Which leads me to my next point

on't attack the AI right away. If he's adjacent to you, build up several stacks of 4 or 5 where you're adjacent, and then one big stack. Then WAIT. Transfer armies, attack neutrals somewhere else, etc. The AI will probably beef up to a big stack next to you, but then he will split it up and attack as many things as he can. If you've defended well, he'll probably lose most of them. As the last thing you do, take your big stack and attack his. He will probably have weakened himself so much you'll win. This is a consistent pattern with the AI, use it to your advantage. If you just build a big stack and attack the AI right off, he probably will have built a bigger stack and you'll lose. Just wait, it will get better.