[Eomer of the Rohirrim]

I think I begin to see your point Saucepan. Sauron would fear what happened to Melkor. Why should he think that the Valar would not intervene and cast Sauron into the void? So it is possible that he created the Rings of power, not just for the domination of Middle-earth, but also to fend off attacks from Valinor.

Probably getting a bit big for his boots methinks.