Ultramarines/Headscratchers

Regarding the film:

 * Space Marine recruits spend years as scouts before becoming full Battle Brothers. How are all these Marines so green that they have never seen combat before?
 * The comic which comes with the special edition actually explains this. They've been very recently promoted from scouts but most of their actions were focused upon recon on the previous world they were on. Severus needed all his best troops to hold the line against a Tryanid invasion and needed a unit to perform a recon mission on the shrine world. Most of the comments about them comes from a lack of experience in full scale battle or true familiarity with some weapons they use.
 * Another possible explanation is that Captain Severus didn't consider them to be Ultramarines until after the rookies graduated from scouthood. Entirely possible that this is their first mission as full Space Marines.
 * It is. They were scouts in the prequel comic. And Severus says this is their first time in combat as Ultramarines, not their first time in combat.
 * So, if they jump to Warp, the daemon will destroy Macragge. Why didn't Ultima squad just head to the bridge and tell them to stop?
 * It's a big ship. They might not have had the time to get there.
 * Also, he's the Captain of the battle barge. He's in overall command. Two newly ordained battle brothers won't be able to override his orders.
 * Why didn't the Imperial Fists fortify their little castle? Since, y'know...it's kind of their thing.
 * Unless Regal Dorn or another Space Marines chapter is actually present, the Imperial Fists tend to fall into the group of chapters that exist solely to get wiped out to show how tough the enemies are. Imperial Worfs?
 * They did fortify it and held against the Black Legion just fine. It was when a Warp Gate opened inside their defensive lines that things got "a little difficult".
 * Remember, we're not looking at the fortress in its prime. We're looking at a fortress that remains after three solid weeks of combat between Space marine/Guard forces and Chaos Space Marines. The fact that anything is left standing at all is a testament to the Imperial Fists' engineering and fortifications.