Two things. Firstly, answered my question and cracked the last level. Solution - take the smaller Harkonnen base and send an Engineer to capture the heavy factory. Access to the Devastator! I simply defended then built up my forces from here. 2 waves at the Emperor's front door - the first is regular Atreides weaponry and takes all units (and possible Harkonnen interference). Not much left to deal with the base proper, but that's where the 2nd wave of 12 Devastators comes in. Their combined blasts destroy everything in record time. Once the Emperor is destroyed, the Harkonnen stay in their base. Build up again (faster this time as you can have a starport in the Emperor's base) and repeat. This way, it was all over in less than a day, and the irony is that the coup de gras is the Harkonnen's own heavy tank. Secondly, yes - this is the Dune 2000 board. Having looked at some of the coversations, I think a few Dune fans that have graduated the Emperor have too high an opinion of themselves. It's just a game.