Based on the observations of Shadow tactics, strategic objectives, and extrapolation of their history prior to the 2nd Shadow War, I have drawn the conclusion that in ages past, the strength of Shadow vessels was considerably greater than in more recent conflicts. This suggests that their newer designs have been deliberately downgraded, and I intend to demonstrate exactly why.
We will begin with what we can extrapolate about the ancient history of The First Ones. Minbari data which was supplied to them from the Vorlons indicated that they and the other First Ones battled the Shadows to a stand-still, ultimately defeating their fleets and forcing them into hiding 10 000 years ago. Considering the Vorlon bias, and the fact that in battles we have seen during recent engagements, the strength of Vorlon ships seem to exceed the Shadows in terms of both firepower and durability, one can thus assume that the Shadows could NOT have held all of the other First Ones at bay on their own. That having been said, I DO intend to show that the strength of the Shadows in those recent engagements CANNOT be used to indicate relative strength during their previous wars.
What we CAN assume is that the conflicts during the countless millennia prior to the war 1000 years ago were considerably broader than the Vorlons let on. I would say that there were just as many First One races allied with the Shadows as with the Vorlons. It stands to reason that their conflicts were brought to a halt when it was revealed that they were wiping out 3rd-Generation races (or Younger Races as they are often referred to) quite unintentionally. I would assume that this revelation would begin as a sort of anti-war movement among the First Ones, either entire races or just representatives of these races, possibly supported by Lorien. When the cease-fire WAS approved and a council of sorts assembled, the eventual solution that was decided upon was the mass but protracted exodus of the various First One races with the condition that two of their number remain to shepherd the Younger Races. This information is not in dispute, though it is likely that the choice of races to remain would be one from each side in the previous conflict as a condition of the peace treaty.
In the several millennia since the end of the First Ones conflict and exodus, both the Vorlons and Shadows would have gotten to work, choosing the various races they intended to shepherd. We DO know that the spirit of the accord was breached sometime prior to the conflict 1000 years ago. The Shadows sought to strengthen their charges by inciting conflict, on a small scale during a race’s early development, such as kingdom-vs-kingdom, moving up to countries and coalitions, and then eventually between colonies out in space. The final stage would be pitting once race against another, though it is unclear if they chose one strong race to eliminate the weak, or if they took evenly-matched races and pitted them against each other allowing races near the bottom of the barrel a chance to move up in the ranks by beating out one on their level. Recent actions with the Centauri, and speculation regarding the Dilgar suggest the former, but that may not have always been the case.
We do know that once the Vorlons became more invested in blocking the Shadows, they somehow made it more difficult for the Shadows to incite war, so their only recourse was to become the threat themselves. The result was the tactics seen in the more recent conflict of killing the weak ones themselves. While this is obviously intended to dispense with the weak, they must also have plans to force the strong to become stronger, and this brings us to the Shadow ships.
The vessels we have seen are strong, but not exceedingly so. They require a biological life form to regulate the ship, which is either already suited to operate a Shadow vessel, or has undergone severe neurological alterations to the same end. It seems though that the Shadows do not trust their subjects to operate the ships on their own, so they perform psychological alterations to eliminate the subject’s free-will so they have no choice but to carry out the will of the Shadows. This cannot have ALWAYS been the case though. It is doubtful that during their pre-accord wars the Shadows would have used subjects from the Younger Races to operate their fleet, but would have rather been operating the ships themselves. When you consider how easily the Vorlons were able to destroy Shadow vessels during the engagement witnessed during “Interludes and Examinations” (S03E15), it is doubtful that the Shadows themselves would have used these classes of ships to fight their wars in, considering how fragile they are compared those of other First Ones.
If this is the case, why would the Shadows deliberately begin using weaker ships? The answer comes down to what they intend on using those ships for. Culling the weak among the younger races wouldn’t’ require the tough and powerful ships they would have used during the pre-accord days, and when trying to force strong races to become stronger, the Shadows would have wanted something not so powerful that it appears insurmountable on a staggering scale. To this end, they downgraded their designs for the Shadow Wars. They would have been powerful enough to outclass anything they would need to face, but still able to be overcome by a determined assault.
This conclusion does leave a few unanswered questions however, like what happened to the Shadows’ ORIGINAL fleet? Was it disbanded as per the Accords… unlikely, since the Vorlon fleet looks to be just as powerful as before. Were they mothballed… perhaps, but then they likely would have made an appearance during the final stages of the most recent Shadow War, when ‘the gloves came off’ so to speak. The most likely possibility, is that they and their shipyards were destroyed by the Vorlons during the last war 1000 years ago. Delenn’s account suggests that the Vorlons and the other remaining First Ones got directly involved once the tide had turned. It is possible that the Vorlons took the opportunity provided by the war to wipe out these forces as that conflict came to a close. With the infrastructure to rebuild this fleet gone, the Shadows were forced to use their downgraded designs to prosecute the next war.
This is of course a theory, but an educated one.