If the option is enabled for the game, island territories receive a limit of armies that can be in that territory at the same time. That island you don't know if it's a territory or just dust on your screen when you zoom out the map entirely? It couldn't hold more than 50 armies, now could it? While that Siberia territory – well... here's where 500 armies would go. Basically what this would do is make your position on the map way more important than it is now. If you're, say, in Antarctica, you wouldn't be able to just put all your armies in a small island, but rather use an airlift card to get them through, or simply move them in small stacks one at a time. If you are in the USA and need to cross the Atlantic Ocean, you won't be able to just annihilate the enemy in Europe simply because you've got 3 times his income. You won't be able to deploy more than, say, 50 armies per island, while he'll be able to deploy 200 armies per territory – just like it's in real life. This would also result in vicious battles for just a single land territory, as this would mean airlift cards could be used to transfer all the armies that are behind the lines – again, just like in real life. This could also eventually result in a new card – something like "Navy support", which would increase the number of armies that you can put in the said territory.