This wouldn't be much of a problem, but my cat spent the early hours of the morning patrolling the front windows against possible threats. He does this every couple of months - presumably because he's seen something scary and bad out there, like another cat. Or a leaf.
It tends to involve increasingly lengthy and loud growling, which eventually turns into the most unearthly noises I've ever heard a cat make. And it is impossible to sleep through.
My general strategy in these situations is to shut him in the laundry (almost windowless, so nothing to growl at) and then leave him there to settle down and go back to bed.
Unfortunately, my laundry is currently full of kittens - who would not be happy being presented with an extremely annoyed cat who wants to attack everything on sight.
Instead, I have got up (at five o'clock) and am sitting with him on my lap while he glares at the world and make periodic attempts to get up and go back to screeching at the window...