I don't know if anyone else noticed this but I was playing a game last week where I was going to invade a two tile island. One tile had a city on it and the other had a radar tower with no one guarding it. I was keen on the island 'cause it had oil so I brought several modern armor to make sure I took the city. Much to my surprise, I wasn't allowed to land on the "empty" tile. I was given the "only marines can make amphibious assaults" message! Whattabunchacrap! On the other hand, I used the same strategy the next game I had a lot of small islands, I didn't have to waste supporting troops on the tiles, I just filled 'em with radar towers. Obviously, the strategy only works if you're not facing berserks or marines.