[quote=Enalais]
Is the empire throwing everything into the ring, like commandos and AT-AT's or so far just imperial army and storm troopers?
[/quote]

Imperial Army and some troops, the lay of the 5 cities makes it hard for bigger transports like AT-ATs to manuever however there will be some in garrisons between the cities. In orbit there is only a couple of light cruisers. More will become apparent when the invasion begins.