I think the problem with Pressman is that he was too close to the machine.
I was going to say that his problem is that he doesn't want peace but victory...he's not a live-and-let-live kind of guy but rather a my-way-or-the-highway. But I don't think you get that high up without being more sophisticated than that - than your success being about just perseverance...Mr. Smith went to Washington and filibustered his throat dry, but it was the repentance of another that triumphed his cause.
At that at that level you can't survive without having more respect for the abilities of your enemy, regardless of how evil you think they are...the Nazi's were evil but it was their strength made victory over them costly, and we would not have pursued it had they not provoked us.
Nor does one achieve and maintain Pressman's rank without being more malleable to the ebbs and flows of life. He may have let the bear get him that day, as Riker would say...he may have made peace...sometimes you let things go so you can fight other fights, and if you're lucky enough, get another crack at enemies that happened to best you before.
So, I don't think Pressman, an admiral of the United Federation of Planets, would have held firm to getting a technological advantage over the Romulans if it meant a) a war of that magnitude, and b) a fundamental shift in Federation values and foreign policy...he may as well have been Palpatine suggesting the Feds reorganize into a Galactic Empire since they momentarily (in the greater sweep of history) had a major tactical advantage.
But I think that with the phase-cloak, Pressman couldn't let the machine go. He had achieved something so inventive, and he had invested so much of himself into it, that he'd lost...
Nope, I take it back. It isn't that the phase-cloak was his baby and he couldn't let go. Earlier in life, he grudgingly civilized himself to get to where he eventually got, but with the phase-cloak, power unlike anything most mortal men could imagine was at his fingertips, and the inner beast tipped the scales.
As I write and reread what I wrote I'm realizing it's been too long since I saw the episode and don't know what Pressman's deal was. I remember two things for certain 1) he was a dick, and 2) thinking the writers went too far with the phase-cloak. It was too advanced. How'd the Feds create it so long ago, and none of the baddies do so since? And if they kept it, it would really change Star Trek forever. And I almost wouldn't mind so one-sided a war with the Romulans.
But for them not to (unless they're total hippie Luddites, of which they're often accused though I don't believe) it must not have been as fundamentally game-changing a device. Heck, I'd have given the Romulans a copy if we could also use it for its peacetime uses.
I imagine that if the Feds kept it, there would be war and the Romulans would Manhattan Project some rudimentary wormhole device of their own to even the scales and there'd be too much senseless destruction.
Written too much. Shutting up now. What do you think?