Why were weapons like Mandrakes and Acromantula, which kill indiscriminately, used in the Battle of Hogwarts?

Question

It seems to me that some of the tactics used by both sides seem a bit questionable. In war you are obviously trying to weaken your opponent whilst minimising collateral damage to your own side. Tactics which hinder both sides equally and which indeed may end up killing more of your own people aren't much use. Which make these passages strange:

He was roused by Professor Sprout, who was thundering past followed by Neville and half a dozen others, all of them wearing earmuffs and carrying what appeared to be large potted plants.
"Mandrakes!" Neville bellowed at Harry over his shoulder as he ran. "Going to lob them over the walls - they won't like this!"
_{(Deathly Hallows, Chapter 31, The Battle of Hogwarts).}

At the same moment, the heavy wooden front doors burst open, and more of the gigantic spiders forced their way into the Entrance Hall.
Screams of terror rent the air: the fighters scattered, Death Eaters and Hogwartians alike, and red and green jets of light flew into the midst of the oncoming monsters...
_{(Deathly Hallows, Chapter 32, The Elder Wand).}

From the Hogwartians point of view, why use Mandrakes? After all,

"The cry of the mandrake is fatal to anyone who hears it.
_{(Chamber of Secrets, Chapter 6, Gilderoy Lockhart).}

The people throwing the Mandrakes may be protected but it seems a clumsy thing to use seeing as there were friendly forces out in the grounds.

"Arthur," he pointed towards Mr Weasley, sitting at the Gryffindor table, "and I will take groups into the grounds."
_{(Deathly Hallows, Chapter 31, The Battle of Hogwarts).}

From the Death Eaters' point of view, why use Acromantula? They seem to have been harnessed somehow under the control of Voldemort's forces. But in the passage above they are clearly posing just as much a risk to the Death Eaters as they are to anybody else. Indeed, their arrival prompts both sides to take up arms temporarily against the spiders in a show of unity. I can understand their usefulness as a siege weapon to cause try and breach the defences and cause havoc within. But there were plenty of Death Eaters in the castle at this stage. Why risk harming friendly troops by using a blunt instrument?

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Note: This related question deals with the effectiveness of the mandrakes, not with whether or not it was wise to deploy them.

Answer 1

It's the same tactics as calling in mortar fire or airstrikes in a battle - to discombobulate the enemy, frighten them, cause them to break ranks and ultimately weaken their forces, as well as cause death and destruction.

There is always the possibility that they can affect your own forces if used incorrectly, but it has a number of advantages for your side over the enemy:

• You ultimately have the initial control over the placement of the weapon. Whilst it can affect your own side, it is more likely that you will affect the enemy more, and at the very worst it will be 50/50. Your side will be at least expecting the method of attack, so can think of ways beforehand to deal with the issue even if it does turn against them.

• It keeps the enemy more frightened and paranoid. If they have only to defend against a single offensive strategy (i.e. spells), they can prepare better. Throw giant spiders or screeching plants into the mix and suddenly they will be off balance trying to deal with a multitude of different threats.

• Facing a group of wizards is dangerous, but getting them to disperse under the assault of heavy weaponry will make them scatter, allowing a much easier time picking them off individually.

For the defenders using mandrakes, they would essentially make no-go areas for their enemies. They could throw them strategically in order to block off vital defensive routes. They could also just throw them at death eaters, forcing them to either scatter or spend time dealing with the mandrake before it killed them or knocked them unconscious.

For attackers using Acromantula, they can send them into the castle where there are many more Hogwartians than death eaters, again causing more trouble for the enemy than themselves, and generally sowing discord in their ranks rather than having to face an organized force.

Answer 2

Mandrakes - The plan was that Sprout, plus some students, would get the appropriate protection on and hurl some Mandrakes at Death Eaters and only at Death Eaters, the idea being that there wouldn't be any Hogwartians in the way.

Acromantula - The idea was to drive them out of the forest and towards the castle, where they would break in and pave the way for the Death Eaters to follow.

The Death Eaters never planned to be in control of them, it's just that there weren't supposed to be any friendly forces in the castle already. If everything had gone according to plan, the Acromantula would have broken into the castle and run into a bunch of Hogwartians, who would have exhausted themselves fighting the spiders. Then, the Death Eaters run in and clean up.

Basically, in both cases, neither side expected friendly fire to be a problem. They had planned for only their enemies to be affected. Unfortunately, it didn't pan out that way and people were in places they weren't supposed to be, right in the line of fire.

Answer 3

From the Death Eaters' point of view, why use Acromantula?

Perhaps because Voldemort doesn't care about the lives of his own troops?

The people throwing the Mandrakes may be protected but it seems a clumsy thing to use seeing as there were friendly forces out in the grounds.

'The grounds' is a huge area. It's entirely plausible for the Mandrakes to be thrown only into areas that are way away from any friendly forces. Also, it should be easy to tell where the friendly forces are, since wizard battles are extremely bright and flashy.

Finally, let's remember that this is J.K. Rowling writing this. She may own a castle, but that doesn't mean she knows how to properly defend one, especially using such exotic weaponry.

Answer 4

I would chalk these sorts of mistakes up to the general chaos of war. People often think they can control the effects of their decisions, then reality does something unexpected and so shows that people are wrong.