AN: Well, that came out sort of weird. The main idea was that Primarchs are huge and sooner or later, wouldn't fit on a normal sized horse.
Size
Jaghatai groans in dismay, as he, quite literally, looks down on his horse. It is only natural that a youth like him will want to grow up quickly, but having this wish be granted is not always convenient. Fa can no longer carry him to battle: he is simply too big and too heavy to ride on her.
What is a warrior without his steed?
A scant two weeks ago, he rode with the other warriors, leading a raid. Now, he could not do it: he has grown out of his horse. It seems so ridiculous. People grow out of their clothes, but horses?
It wouldn't worry him so much if he weren't so certain he is still growing. Already, he has trouble entering yurts and moving around in them. While not clumsy in the least, there is no day when he does not collide with something or, in one embarrassing case, somebody. The only bright side he can find is that he practically doesn't bruise and hardly ever loses his balance.
He reaches out to pat the animal's chestnut neck. It's a familiar gesture and he smiles. He is still upset that he cannot ride on Fa anymore, but he has an idea. It will take time, but he thinks he will be able to ride a horse again in the future.
After all, he reasons, horses are already bred to enhance certain physical features. Simply adding size and strength to the mix should not pose a problem. It is time that worries him. After all, he needs to essentially create a new breed and that will take decades. Besides, he will be the only one riding those horses: convincing others to the idea will not be easy.
His expression falters and he frowns again. While he is certain he will live long enough to ride on the beasts, he intends to breed, he's also quite certain that somebody will remind him that accidents happen and he could die tomorrow. How can he be sure he'll be alive in forty years? Of course, he knows that it's all nonsense. If nothing has managed to cause him serious harm so far, why should it happen in the future? But he still needs a different counter argument, because somebody will surely grumble that young people always think they're immortal.
That's not as easy to come up with. He busies himself with cleaning his horse as he thinks. Idly, he wonders about the design of the brush and who came up with it, since he has no inspiration regarding his earlier problem.
Then he inspects the legs and cleans the hooves. There seems to be nothing to worry about; he muses that it really is a pity. Fa is a fine horse and since he can't ride on her, she won't see any more fights.
If he were old enough to have a son…
He looks up, a thoughtful expression crossing his face. Slowly, he stands up straight and absently pats the horse's side. The problematic counter-argument to his plan of breeding horses returns to his mind, but this time it doesn't seem as troubling.
Children tend to take after their parents. Tall parents have tall children. Since he's huge, he reasons, he will have huge children, who will need large horses. While he isn't really interested in procreation, he thinks that pointing out this will shut up any complaints about his theoretical lifespan.
Satisfied with his reasoning, he heads back to discuss his idea. A warrior needs a good horse, after all.