How do the dragons exactly know whom/what to burn?

Question

When Daenerys says "Dracarys" in Game of Thrones, the dragons almost always hit the target on point.

In Season 8, Episode 5, when Dany says "Dracarys", Drogon kills Varys by fire. But there were many people nearby, how did Drogon know who exactly to "Dracarys" ? What if he burned someone else by mistake ? What if Tyrion died or any of the soldiers?

Are the Dragons and Dany's mind connected so that the dragons know exactly whom/what to burn and how much firepower is required?

How does Dracarys work?

Mind connected example: In book Eragon, the dragon and the protagonist talk to each other in their minds

Answer 1

Yes, there is a supernatural bonding between dragons and their masters:

• [..] dragons appear to have some sort of higher, unnatural level of intelligence; they seem to be more in tune with "magic" (or "fate" or "nature") than humans are, and possess a sense of mental awareness that humans do not. Somehow, they are often able to sense when the human rider they are bonded with needs them.

  They can form very strong bonds with their riders and will show affection and trust towards them. They will even nuzzle their riders, hoping to be petted.

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  Dragons are intelligent, more intelligent than men according to some Maesters. They have affection for their friends and fury for their enemies.

  ^{Tyrion Lannister, s06e02}

  This "mental awareness" could easily account for the sensitivity with which the dragons follow orders, and discern friend from foe.

Dragons are able to understand basic orders.

• They can understand voice commands from humans, [but] no more than what a dog or a horse can do.

  Dragons are intelligent animals, and like a horse or a dog, they can be trained by their rider to respond to basic voice commands.

  Daenerys Targaryen has trained her three dragons to respond to vocal commands in her mother tongue of High Valyrian. She often uses the command "Dracarys", to which her dragons respond by instantly breathing fire and burning anything in their path.

  This seems to work like training a dog to 'seek', for example.

  And like a dog can learn to grab limbs but not bite through, so dragons will instinctively know how much firepower is needed to accomplish a certain goal. As an innate ability, I can imagine them having so much control over the shaping of fire in their mouths, they can control flow, amount, direction, pattern, etc.

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As a side note, there are clear limitations to the control humans have over dragons, and they will retain their own will and wit.

• Since they cannot be truly tamed, dragons can be very dangerous even to their riders.

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  They're dragons, Khaleesi. They can't be tamed...not even by their mother.

  ^{Jorah Mormont, s04e01}

  This autonomy is amplified in times of lack of food, for example:

  The key to training dragons is making sure they are well fed, a dragon with a full stomach is more obedient.

  It is suggested that was the reason Daenerys taught her dragons the command 'Dracarys' in the first place:

  Daenerys tries unsuccessfully to feed her dragons raw meat, unsure of what she is doing wrong. Later, in Qarth, she realizes that they will only eat cooked meat. She coaxes them into recognizing the Valyrian command, "Dracarys," to breathe fire, so they can cook their own food.

^{For my research in this matter I have drawn heavily from Maester Fandom's Scrolls of the Serpent.}