Apex Predators Do Not Take On Herds

And an army is a very well trained, resilient herd with many spears. Every predator is looking to get the easiest meal they can, so they are looking for stragglers or to isolate individuals. This is actually similar to armies, which also want to isolate smaller sections of their enemies and pick off stragglers. Instead of eating, though, armies are looking to control territory.

But Military Operations!

These will hardly change, there is just another threat to worry about. Good commanders secure and protect supply lines, even against apex predators. Smaller forces (or Hannibal) can raid and pillage to sustain themselves.

An Exception: Kaiju

In which case, everyone dies anyways and war is not part of your story!

If the predator is large enough that no combination or number of medieval weapons or poisons can harm them, mankind has bigger problems than fighting each other. It's an apocalypse and no one is waging formal war. Maybe raids and small groups/tribes, but not massive and organized war. War in the time of Kaiju, though intriguing, usually isn't the point of Kaiju stories.

Apex Predators Do Not Take On Herds

And an army is a very well trained, resilient herd with many spears. Every predator is looking to get the easiest meal they can, so they are looking for stragglers or to isolate individuals. This is actually similar to armies, which also want to isolate smaller sections of their enemies and pick off stragglers. Instead of eating, though, armies are looking to control territory.

But Military Operations!

These will hardly change, there is just another threat to worry about. Good commanders secure and protect supply lines, even against apex predators. Smaller forces (or Hannibal) can raid and pillage to sustain themselves.

An Exception: Kaiju

In which case, everyone dies anyways and war is not part of your story!

If the predator is large enough that no combination or number of medieval weapons or poisons can harm them, mankind has bigger problems than fighting each other. It's an apocalypse and no one is waging formal war. Maybe raids and small groups/tribes, but not massive and organized war. War in the time of Kaiju, though intriguing, usually isn't the point of Kaiju stories.

Edit: From comments, I suppose I should clarify this section. I use Kaiju for their "unstoppable, uncontrollable force" aspect. Kaiju represent the most extreme case of a predator. If a predator has such qualities, we are looking at a breakdown of society in proportion to the predator's appetite. The question is very details light, but I feel like I had to account for such a situation but also point out that wartime logistics and strategy is unusual for the Kaiju genre. Arguably, these stories are about big monster battles ("spectacle"), distruction, forces beyond mortal control, and/or forces which shouldn't be in mortal control. (Original Godzilla, in context of Japanese culture at the time, sure does look like a stand in for nuclear weapons.)

Apex Predators Do Not Take On Herds

And an army is a very well trained, resilient herd with many spears. Every predator is looking to get the easiest meal they can, so they are looking for stragglers or to isolate individuals. This is actually similar to armies, which also want to isolate smaller sections of their enemies and pick off stragglers. Instead of eating, though, armies are looking to control territory.

But Military Operations!

These will hardly change, there is just another threat to worry about. Good commanders secure and protect supply lines, even against apex predators. Smaller forces (or Hannibal) can raid and pillage to sustain themselves.

An Exception: Kaiju

In which case, everyone dies anyways and war is not part of your story!

If the predator is large enough that no combination or number of medieval weapons or poisons can harm them, mankind has bigger problems than fighting each other. It's an apocalypse and no one is waging formal war. War in the time of Kaiju, though intriguing, usually isn't the point of Kaiju stories.

Apex Predators Do Not Take On Herds

And an army is a very well trained, resilient herd with many spears. Every predator is looking to get the easiest meal they can, so they are looking for stragglers or to isolate individuals. This is actually similar to armies, which also want to isolate smaller sections of their enemies and pick off stragglers. Instead of eating, though, armies are looking to control territory.

But Military Operations!

These will hardly change, there is just another threat to worry about. Good commanders secure and protect supply lines, even against apex predators. Smaller forces (or Hannibal) can raid and pillage to sustain themselves.

An Exception: Kaiju

In which case, everyone dies anyways and war is not part of your story!

If the predator is large enough that no combination or number of medieval weapons or poisons can harm them, mankind has bigger problems than fighting each other. It's an apocalypse and no one is waging formal war. Maybe raids and small groups/tribes, but not massive and organized war. War in the time of Kaiju, though intriguing, usually isn't the point of Kaiju stories.

Apex Predators Do Not Take On Herds

And an army is a very well trained, resilient herd with many spears. Every predator is looking to get the easiest meal they can, so they are looking for stragglers or to isolate individuals. This is actually similar to armies, which also want to isolate smaller sections of their enemies and pick off stragglers. Instead of eating, though, armies are looking to control territory.

But Military Operations!

These will hardly change, there is just another threat to worry about. Good commanders secure and protect supply lines, even against apex predators. Smaller forces (or Hannibal) can raid and pillage to sustain themselves.

An Exception: Kaiju

In which case, everyone dies anyways.

If the predator is large enough that no combination of medieval weapons can harm them, mankind has bigger problems than fighting each other. It's an apocalypse and no one is waging formal war.

Apex Predators Do Not Take On Herds

And an army is a very well trained, resilient herd with many spears. Every predator is looking to get the easiest meal they can, so they are looking for stragglers or to isolate individuals. This is actually similar to armies, which also want to isolate smaller sections of their enemies and pick off stragglers. Instead of eating, though, armies are looking to control territory.

But Military Operations!

These will hardly change, there is just another threat to worry about. Good commanders secure and protect supply lines, even against apex predators. Smaller forces (or Hannibal) can raid and pillage to sustain themselves.

An Exception: Kaiju

In which case, everyone dies anyways and war is not part of your story!

If the predator is large enough that no combination or number of medieval weapons or poisons can harm them, mankind has bigger problems than fighting each other. It's an apocalypse and no one is waging formal war. War in the time of Kaiju, though intriguing, usually isn't the point of Kaiju stories.