Operation Ikarus was the German plan in WWII to invade Iceland. The plan wasn't realized for many a reason, not in the least the death of the sea-mammal-that-must-not-be-named.
Your challenge is to make an Operation Ikarus that would be viable to the German leadership and actually carried out. It's OK to have the Germans be crushed within a few months by an American invasion, but what would such a plan look like, and what would the combat be like?