In "Balance Of Terror", 1. season of TOS, the Enterprise investigates the lack of response from Earth outposts 2 and 3 (and subsequently 8) monitoring the Neutral Zone between planets Romulus and Remus and the rest of the galaxy. Using his authority as a ship's captain, Kirk is preparing to solemnize the marriage of crew members Angela Martine and Robert Tomlinson. However, the ceremony is interrupted when Earth outpost 4 reports itself under attack by an unknown space vessel.
Spock: "a line of Earth outpost stations. Constructed on asteroids, they monitor the Neutral Zone established by treaty after the Earth-Romulan conflict a century ago. As you may recall, this conflict was fought, by 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. [...] The treaty, set by sub-space radio, established this Neutral Zone, entry into which by either side would constitute an act of war. The treaty has been unbroken since that time." (2265)
And from TNG's 3rd season, The Defector, we know, that the "Treaty of Algeron" established the Neutral Zone. It has been negotiated via subspace radio and provides that "entry into the zone by either party would constitute an act of war".
This treaty was also mentioned in the 7th season of TNG (The Pegasus).
It was a war between Earth and the Romulans - no federation! The techniques, which were used, were very primitve. Therefor it happened before the founding of the United Federation of Planets, which was in the year 2161.
Again from Star Trek V:
Nimbus III was colonized by Romulans, Klingons and the Federation twenty
years ago.
And the planet must have been colonzied after the first face-to-face-contact
between the Romulan Empire and the Federation, which took place in the
first season TOS: 2265.
The "twenty years ago" from above could be understood as "between 17 and
23 years ago".
StarTrek V is laid 2285. The colonization of
Nimbus III would therefore happend (2285 - 17/23=) between 2261 and 2268.
Everything before 2265 is too early, because that would be before the
first face-to-face-contact with the Romulans. Therefore Nimbus was colonized
between 2265 and 2268.
Also from Star Trek VI. is the statement, that the Organian-Peace-Treaty is twenty years old. (p. 21)
We can read this as "between 17 and 23 years ago" and can count back from 2295/2296. Therefore the signment took place sometimes between 2271 and 2279. The Organia-Incident happend in TOS 1st season, which was before TOS 2nd season, which means before the year 2266.
Therefore there is a signed Peace-Treaty named after Organia IV, which was signed 10 years that war. (The Organians forced the two powers to end a war. But nothing was signed at that point. Later on they must have met - maybe on Organia?)
