Splitting maul, two wedges and a sledge.
Many years ago my Dad got about a cord of red oak rounds delivered for firewood. They were about 18" to 20" long and varied from 10" to 24" in diameter. We used a 5 lb. splitting maul for most of them. He taught me how to read the grain in the rounds to use that to my advantage. You just look for the natural way the rings are in the round and try to follow them to help split them. If they had any natural cracks in them, that was an aiming spot to split them.
Some just refused to die...we got two splitting wedges and a 5 or 6 lb. sledge for them. You'll find you will need a large wedge and a smaller one to work with. You'll get one wedge hopelessly stuck in the round and will need a second wedge to get it out. Trust me, I speak from experience. A splitting maul can be used for a wedge if needed, using a sledge to drive it, but that is not what it is intended for.
If you get a splitting maul make sure the sledge end is hardened, as it can help you out with getting stuck wedges out.
Use the grain and any natural cracks in the round to your advantage. As you go along, it will get easier to "read" the end of a round. It will work for all types of rounds.
Hope that this helps you out...Good luck.
Double Ott aka; Tom; TC
Vintage PUMAs from the 1970's & 1980's.. Let me know what you have, Thanks