Why was Smaug able to take over Erebor with such ease?

Question

The dwarves of Erebor were a powerful nation who were well aware of the existence of dragons (and their relative proximity to the Withered Heath). Despite vast resources, of both time and money, they seem however to have been entirely unprepared to handle the attack by Smaug (who also destroyed Dale at the same time). Furthermore, the Smaug who defeated Erebor at this time was a far weaker serpent than the one who is killed during The Hobbit (describing himself as being smaller and with a vulnerable belly).

So why did Smaug have such a one-sided victory?

Answer 1

In the source novel, we see most of the Dwarf warriors killed in three separate engagements. Smaug has nearly total air superiority and is well able to use the nearby environment to create ambushes, choke-points and distractions, all signs of a master tactician.

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Firstly, he announced his presence by setting light to the nearby forest. Undoubtedly this would have resulted in smoke, flames and confusion (as well as preventing its use as an escape route or a route for reinforcements).

Some of the dwarves who happened to be outside (I was one luckily -a fine adventurous lad in those days, always wandering about, and it saved my life that day)- well, from a good way off we saw the dragon settle on our mountain in a spout of flame. Then he came down the slopes and when he reached the woods they all went up in fire.

He ambushed the Dwarf warriors who came out of the main gate of Erebor.

By that time all the bells were ringing in Dale and the warriors were arming. The dwarves rushed out of their great gate; but there was the dragon waiting for them. None escaped that way.

Then he created a fog to allow him to ambush the warriors of Dale.

The river rushed up in steam and a fog fell on Dale, and in the fog the dragon came on them and destroyed most of the warriors - the usual unhappy story, it was only too common in those days.

At that point it was merely a mopping-up exercise. No single warrior could possibly hope to best him in single combat given his fiery breath, impenetrable scales and speed.

Then he went back and crept in through the Front Gate and routed out all the halls, and lanes, and tunnels, alleys, cellars, mansions and passages. After that there were no dwarves left alive inside, and he took all their wealth for himself.