Why did Izetta use Blood Magic? As demonstrated several times, Izetta's power appears to revolve around her being able to touch objects and impart her magic into them. Since blood is part of her body, she was able to use her blood as an extension of herself to indirectly touch the snow on the mountain to create the ice lances. Since blood still counts are 'part' of her, it was fair game.
Why does Izetta talk to objects she manipulates? When she manipulates objects she touches, she makes them a 'part' of her which is why she treats them as living things and talks to them.
Why is Izetta unable to use her magic to make tanks and rifles fire? Izetta's abilities allow her to levitate and/or manipulate their movements, but that doesn't mean she has the ability to affect their mechanisms which is why she has to still pull the trigger herself or have the tanks crash into each other.
Finé's Decisions
Why was Finé reluctant to accept Izetta's help? As seen in the first episode, Finé has proven to be politically savvy. She understands the long term consequences of actions which is why she made sure other potential heirs to the throne were available before she made her decisions in the first episode since it would involve giving up her claim. She understood that if Izetta used her power, it would expose her existence to other countries that would want to use her power and wouldn't care about her as a person. Not only was Finé concerned about whether her friend would be killed in battle, she was also concerned that her friend might end up painting a target on the back of her head even after the war is over since other countries would want to study and/or manipulate her power. Finé understands that Izetta could very well be signing her own death warrant for choosing to help her country.
After Izetta made her decision, Finé took action of her own and contacted her soldiers. She did that not only because she decided to honor her friend's decision and increase the chances of Izetta surviving the battle, but she did it to politically legitimize Izetta's actions. After informing her men Izetta was definitely on their side, it not only increase morale, but it united was was left of the forces behind Izetta's offensive. Additionally, Finé understands that this might be Izetta's best chance of survival if she can find at least one safe haven that can accept her. The best chance for that is through unifying her people behind Izetta.
Other
A combination of Bilingual Bonus and Genius Bonus: the flying bombs powered by the revenge-obsessed Sophie are expies of Nazi Germany's V1 bombs. The 'V' in V1 stands for Vergeltungswaffe: 'weapon of vengeance'.
Fridge Horror
When young Izetta suffers a brief bout of Power Incontinence during the Witch Hunt flashback, she accidentally summons some glowing red crystal into her hand: crude Hexenium. She came very close to accidentally Fantastic Nuking the place, and quite possibly herself with it. Thank you again, Finé, for helping avert that outcome!
From the finale: In this Alternate Universe, World War II ends in December of 1941 after heavy and coordinated assault by on Germania by Atlanta, the European Allies and the Volga Federation. In our universe, the attack on Pearl Harbor took place that very same month. If Izetta's world has an equivalent to Imperial Japan, there's a good chance that, with Atlanta's troops and industrial might focused on the other side of the globe, her holdings in the Pacific will form an even more tempting target. Europe may be headed for peace, but there's a good chance the United States of Atlanta are headed straight into a second war, half a word away.
This universe separates the Germanian Empire from their Alt-Japan with an extremely rapid, magic-based technological development that outpaced WWII's actual progression. It seems that the War in Europe resolved before the War in the Pacific started. However, the finale episode does show a survived Bergman handing off Germanian technology to the Atlantans in exchange for asylum while Fíne talks about another war brewing soon. Those plans include designs for V1 and V2 rocket equivalents and a Trinity-style Fantastic Nuke design. - Gwennie-chan
On another note, only the ley line network for Europe is ever shown. Did Izetta's reach with the Magic Stone extend to the entire globe, or only across the continent? In the latter case, there may well be other witches out there still capable of using their powers. Sure, Europe will be one giant Anti-Magic zone, but there's going to be very little stopping, say, Izetta-verse Japan from recruiting their own witch and going to town on Asia and the Pacific. Particularly since Izetta and Sophie have demonstrated the enormous strategic value of witches...
