Sometime early in the Second Cycle, around the 3rd Cbluvoe (3/12/2/16/5/17/12/4/9 to give the exact date given by the Forerunners themselves - through with what degree of accuracy is only speculative), the Forerunners finally "cracked" the FTL drive problem. Within a century or so they began to spread rapidly throughout "Homespace" (a speculative translation of a double Glyph including the Glyph for "Home", the Forerunner home planet). It was sometime during this period that they made contact with several other intelligent races. Evidently, these racial group had not, at the time of contact, even discovered the crudest methods of Reaction powered spaceflight ( according to Forerunner sources).
The Forerunners evidently were overjoyed to discover that they were not alone in the universe, and began immediately to modernise these newly discovered societies in an attempt to bring them the full benefits of advanced scientific technologies. In the next several hundred years, this process was repeated many times. Then, suddenly, it was stopped - for no reason that we can determine from the information available. The only clue that we have is that several of the contacted races cease to be mentioned in any later Forerunner texts, even their homeworlds are no longer referred to; of the rest, they gradually drop out of "sight" for several Terran years before they are mentioned again; and when they are, they seem to be strangely behind in their Technology when compared to their Forerunners Mentors.
During this mysterious lapse in the records of previously contacted races, there also a dearth of NEWLY discovered races being mentioned. Perhaps significantly, the handful that ARE all seem to have developed at least Reaction powered Spacecraft, and the great majority had developed TISA Drives, one or two seem to have developed crude FTL drives and seem to have discovered the Forerunners themselves on their first voyages.
These contacts were evidently not always peaceful - and several seem to have involved relatively prolonged periods of warfare (the longest being almost 9 Uvoe - about 17 Terran standard years) - before the hostile races were either conquered or sought peace treaties. However, the Forerunners always seems to have treated their ex-enemies with the utmost fairness and an extreme degree of sensitivity. This was evidently so successful that by the later part of the second Cycle, the Forerunners and their Allies formed a "Council of the Worlds of Space" (literally; perhaps "Interstellar Council" would be a closer rendition) with seems to have developed into a fully fledged Interstellar government.
One of the first policies that the Council adopted - and the ONLY one recorded in any of our sources - was that a newly discovered race was to be strictly left alone UNLESS or UNTIL it developed a form of Spaceflight and was deemed by the Council's "Adjustors" to be stable enough to have the existence of a community of starfaring races revealed to it. There is some speculation that this resolution is given so much prominence because of some connection with the mysterious lapse in contact (sometimes permanent) with some of the first races discovered by the Forerunners, though the connection is purely theoretical and speculative.
For the rest of the second and third Cycles, as far as we can tell, almost all the fourth Cycle, there was a time of total peace. This was marked by a fairly rapid expansion of the races belonging to the Interstellar Council throughout a sphere of space evidently several hundred LY in diameter ( and hundreds of thousands of Cubic LY) - highlighted now and then by brief conflicts (they rarely lasted long enough to be called "wars") with some newly discovered races. The whole era was one of unprecedented peace, prosperity, and technological advancement to heights we still cannot be entirely sure are factual, and not later fantastic accretions.
However, all is not as rosy a picture as the texts and other sources we have paint. In fact, as we will see in the next section, the whole era was doomed to collapse.