Isn't the other end supposed to be secured to something ?
It's happened again and once again my golden prose has disappeared down the electronic plughole and so I'll repeat the gist of it.
The chain was lost because, whatever the cause, it's weight took over and it ran away. Anchor chains are always run out under power/brake to maintain control unless it is a dire emergency and all control has been lost.
My guess is that the chain was 3" stud-link and 14 shots went overside. (1 shot = 15 fathoms) A shot of 3" weighs about 8,000lb and thus the chain that went out was ca. 50 tons plus the anchor. That sort of weight running at 3' - 4' per second is going to generate a helluva lot of kinetic energy. You may have a big fat padeye in the chain locker to secure the bitter end of the chain to but if you expect it to resist the force then you are going to have to beef up the plate to which the padeye is secured and then the scantlings of the structural members that support that and so on and so on. Thus the reason for fitting a weak link between the chain and the padeye. In extremis, the weak link parts and the chain goes overside but the locker structural integrity remains intact.
I am unable to check it out for the moment but a weak link may well be a Classification Society requirement although, of course, warships are not built to Class but have their own standards.
I'm not sure what type of vessel the above drawing refers to but the idea of going into a locker and removing the split pin and thus the retaining pin from the chain "in emergency" is definitely one to file under "After you Claude; no after you Cecil".
By the by, I always understood 'bitts' to be deck furniture used for mooring.
Barry M