In this post I will try my hand at reconciling 'Balance of terror' with Ent and the rest of trek.
The relevant lines from 'Balance of terror':
1 "SPOCK: this conflict was fought,[...] By our standards today, with primitive atomic weapons and in primitive space vessels[...]Which allowed no quarter, no captives. Nor was there even ship-to-ship visual communication. Therefore, no human, Romulan, or ally has ever seen the other."
The war was fought with primitive ships only when compared to the 23rd century ones
. This is supported by Ent: 'In a mirror, darkly' 1,2, where the technological difference between said periods is shown.
Indeed, an interstellar starship cannot be considered 'primitive' in another sense: its builders need to have an exact idea of the physical laws and be advanced in a variety of engineering fields.
There were no ground battles
; no seeing your enemy on the battlefield. One limitation necessarily imposed by 'Balance of terror'.
The romulans used mostly warp capable drone ships
- 'no prisoners to capture, no bodies to recover'.
Not remote controlled as in Ent: 'The Aenar' trilogy; the dramatic potential of this concept was exhausted there.
Instead, the drone ships are equipped with AIs; a Lovecraftian enemy
, accomplishing the missions with no hesitation or regret - they don't have for them useless visual communications installed.
There may be some conventional romulan ships present during the war - which have as policy self-destruction when incapacitated.
The romulan strategy - nuclear extermination of the worlds they captured
; not occupation or something similar.
2 About the cloak. 'Balance of terror':
"KIRK: I don't see anything. I can't understand it.
SPOCK: Invisibility is theoretically possible, Captain, with selective bending of light. But the power cost is enormous. They may have solved that problem."
Ent establishes heavy suliban use of the cloak; it also establishes that the romulans have cloaking and are not shy in using it.
By necessity, this means that Kirk, Spock&co were not well read on this issue. Now - the name of the game is excusing Kirk, Spock&co's lack of knowledge on the cloak subject
without making them look like incult fools who don't know their history.
Let's see - Ent also establishes that Daniels gave Archer a technology able to see easily through suliban cloak.
I can posit that, at the beginning of the war, there was some cloak use by the romulans. The Federation, early in the war, perhaps building on Daniels gift, created a foolproof way of seeing through the romulan cloak
, rendering it useless.
So foolproof, that Federation experts assumed the cloaking technology has no future
. As such, in the decades that followed, there was no attempt by the Federation to perfect the cloaking technology; indeed, it remained known only to a small nostalgic fringe
, to which, Kirk, Spock&co didn't belong.
The romulans, on the other hand, did not give up on the cloak. After decades of trying, they created one that hid - somewhat - their ships from starfleet sensors - as per 'Balance of terror'.
After said episode, the Federation became interested enough to capture a cloak, perhaps even outfit a few of its ships with reverse engineered cloaks.
Fundamentally, though, based on how thoroughly the cloak was overcome during the War, experts in the Federation remained convinced that this new type of cloak will soon be thoroughly defeated, returning to being as obsolete as it used to be.
As such, the Federation was not interested in pursuing the technology. At the Treaty of Algeron
, the Federation renounced what it saw as a dead-end technology.
Needless to say, the Federation "experts" who made this determination were wrong. Disastrously so. As such, a century later, the Federation is severely handicapped by the legally binding interdiction in building, perfecting or using cloaks.