What dimensions must a dragon have, in order to make cutting off their heads with a sideways axe swing a plausible method of killing them?
When I say plausible I mean (a) the axe can physically cut through the dragon's neck and (b) the axeman has enough time to swing before he is eaten.
Suppose I want to write some sort of parody or homage to "The 51st Dragon" by Heywood Broun.
https://zameroskiwebpage.weebly.com/uploads/1/3/3/2/13324979/the_51st_dragon.pdf
Suppose that there is a character who sympathizes with the timid and cowardly Gawaine le Coeur-hardy and thinks that Gawaine has a right to be timid. The character may believe that the knight school is wrong to teach boys to be brave and fearless, since in their experience the majority of brave men use their bravery to do evil instead of good. In fact the main occasion for men to do good with bravery is when fighting the evil deeds of other brave men. If no men were brave, there would be no need for good men to be brave to fight the evil brave men. So they consider the whole purpose of knight school to be warped and evil.
Anyway, in Broun's story the headmaster assigns Gawaine to slay dragons. So they try to teach Gawaine about dragons, and make him practice beheading dummy dragons with an ax, making the dummy dragon necks with harder and harder materials until Gawaine seems strong enough to cut off a real dragon head with one swing of his ax.
And beheading a live and unwilling dragon with an ax seems rather improbable.
Up until recent centuries European nobles had the right to beheaded instead of hanged like commoners when being executed.
And in some times and places they were beheaded by beheading machines which were early forerunners of the guillotine.
And sometimes they were beheaded with swords. The condemned would sit in a chair or kneel and the headsman would swing the sword horizontally at the victim's neck, usually taking off the head with one swing. After cutting through bone the sword would have to be resharpened before the next swing.
And possibly the most often they would be beheaded with axes. the condemned would get down on all fours and lay their neck on a chopping block and the executioner would stand to the side of the chopping block, raise the ax, and then swing it downwards, or perhaps let gravity pull it downwards, usually cutting the head off in one stroke.
I once saw somewhere on the internet the drawing of a beheading, which looked very inaccurate. I doubt that the artist knew anything about beheadings. This was supposed to be the beheading of Sigurd Sigurdsson Markusfostre, illegitimate son of Sigurd II and rival king of Norway, probably aged somewhere between 8 and 16 years old.
In the drawing, young Sigurd is kneeling, which is the right posture to use when being beheaded with a sword. But the executioner is shown swinging an ax. Since Sigurd's neck is not touching a chopping block to keep it in place, when an ax hits it from one side it will push Sigurd over onto his side and possibly not penetrate very far into the neck. Furthermore the executioner is shown swinging the ax rather wildly with one hand if I remember correctly. I am not certain which direction the ax is being swung in.
Anyway, the normal use of a war ax is to raise it over your head and swing it downwards, I think. Medieval reenactors can correct me on this if I am wrong. I doubt that someone could swing an ax sideways with as much force as in a downward swing.
Note that Gawaine is not taught to swing the ax down on the dragon's skull and split the skull open.
The easy way to chop off the head of a dummy dragon would be stand beside the neck and swing the ax down on the neck.
And in the story, dragons charge at Gawaine and he swings his ax - up or down as the case may be - at their necks and chops off their heads. So when Gawain swings, the dragons are facing him and he is facing them. He can't swing his ax on their necks from the side because he isn't beside their necks but in front of their heads.
So Gawaine has to swing his ax sideways to get at the dragon necks. Gawaine is a big strong boy but if he swings his ax directly sideways so he hits the dragon necks at a right angle for the easiest cut he has to fit the dragon head - not yet touching him - and the part-off the neck where he cuts, within about two or two and an half feet of him. If a dragon's head is five feet or ten feet long a striking dragon will bite Gawaine long before the dragon's neck is within Gawaine's reach and the dragon will kill Gawaine.
When Lady Jane Grey, the teenage 9 day queen of England, was being beheaded in 1553:
She then blindfolded herself. Jane then failed to find the block with her hands, and cried, "What shall I do? Where is it?" Probably Sir Thomas Brydges, the Deputy Lieutenant of the Tower, helped her find her way. With her head on the block,...
https://en.wikipedia.org/wiki/Lady_Jane_Grey#Trial_and_execution
So Jane, like most people being beheaded, cooperated with the executioner, instead of fighting the headsman or even trying to eat him like the dragons tried to eat Gawaine when he beheaded them.
And to me it seems a lot easier to hit the neck of someone standing still and cooperating in their execution than to hit the neck of a dragon darting their head at you in an attempt to eat you.
Maybe in the practice trials they put mockups of dragon heads and necks on carts and pushed them at Gawaine, pushing them faster and faster each time until he could chop off a head coming at him as fast as a lunging dragon's head.
If Gawain was being charged by a lion, or a tiger, or a bear, or a hippo, or a rhino, or a crocodile, or an elephant, could he chop off the head in time? Or would the head merely be pushed sideways by the ax, and Gawaine be knocked down by the critter and killed before he could swing again? Would the neck be thin and weak enough for Gawaine to cut it off in one sideways swing? Would the head be short enough that Gawaine could reach the neck and cut off the head before the front of the head reached Gawaine and killed him?
I find Gawaine's ability to kill large real animals and survive their attacks rather dubious.
So how big are the dragons in "The 51st Dragon" compared to lions, tigers, bears, hippos, rhinos, crocs, and elephants?
“They say that those dragons down in the south wood are five hundred feet long,” ventured Gawaine, timorously.
“Stuff and nonsense!” said the Headmaster. “The curate saw one last week from the top of Arthur’s Hill. The dragon was sunning himself down in the valley. The curate didn’t have an opportunity to look at him very long because he felt it was his duty to hurry back to make a report to me. He said the monster, or shall I say, the big lizard?—wasn’t an inch over two hundred feet.
Here is a link to the J.R.R. Tolkien painting, "Conversation With Smaug":
https://bodleianshop.co.uk/products/conversation-with-smaug-notecard
By using a ruler to measure short lengths along Smaug's body, you should find that Smaug's total length is about 40 times the width across Smaug's pair of nostrils, like I did when I was a child. So if Smaug is 200 feet long, as I calculated when I was a child, he should be 5 feet wide across his nostrils. Which makes Smaug's head roughly about 18 feet long, and Smaug's neck right behind the head about six feet thick. Smaug is built a lot more slender in this painting than the typical depiction of a dragon.
So if Gawaine tried to behead a lunging dragon which was both 200 feet long and build like the exceptionally slender Smaug, Gawaine would be swallowed whole before he could reach the dragon's neck with his ax, and one swing of his ax would not be enough to cut the head off the six foot thick neck anyway. The problem would be much harder with a dragon in a typical depiction.
So I guess that if the dragons in "The 51st Dragon" to be 200 feet long or more they would have to be very, very, very slender, even compared to Smaug, who is exceptionally slender compared to most illustrations of dragons.
A 200 foot long dragon who was beheadable by a human would have to have a neck not much thicker at the point of beheading than a human neck. And the head would have to be 2 feet long or less for the human to be able to reach the neck before the front of the head reached the human.
So is there any known snake or lizard which has a head less than 1 percent of their total length long, and a neck which is less than 0.5 percent of their total length thick? A animal which might be a model from which the dragons in "The 51st Dragon" could be scaled up?
Or:
Which plausible method - if there is any - of slaying a 200 foot long dragon would be the closest to Gawaine's method?
Or:
How small would dragons have to be for cutting off their heads with a sideways ax swing to be a plausible method of killing them?