Radio Estros episode 74 in conjunction with history of Westeros the Dance of the Dragons

Part 5.

Spoils All Books. A dragon's scales are largely though not entirely impervious to flame.

They protect the more vulnerable flesh and musculature beneath.

As a dragon ages, its scales thicken and grow harder, affording even more protection,

even as its flames burn hotter and fiercer.

Where the flames of a hatchling can set straw of fire,

the flames of Ballerian and Vager in the fullness of their power

could and did melt steel and stone.

When two dragons meet in mortal combat therefore,

they will often employ weapons other than their flame,

claws black as iron, long as swords, and sharp as raisers,

jaws so powerful they can crunch through even a night's steel plate.

Tails like whips, who's lashing... through even a night's steel plate,

tales like whips whose lashing blows have been known

to smash wagons to splinters,

break the spine of heavy destriers,

and send men flying 50 feet in the air.

The Knight is the standard dominant marshal figure of Westeros and has been for eons now.

This quote shows us that the warrior class is completely outclassed by

dragons who, minus the occasional lucky shot from a scorpion or the like have no threats to fear except from each other.

None of this is an exaggeration as far as we can tell either. We saw Drogon break the back of a wild horse and he's a young dragon.

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