During the 2290's, Starfleet was in dire need of new starship hulls. The aging Constitution-class Cruisers were nearing the end of their useful lives while production of the new Excelsior Heavy Cruiser remained too low to fill the niche left by them in the field. Starfleet put out several requests for proposals among the leading shipyards, and several bids were accepted to help and fill the gap, as the production was viewed as nothing more than a stop-gap initiative.
One of the first classes to go from the drawing board to the fleet yards was the Vigilant Light Cruiser. Using design elements taken from the successful Excelsior, the Vigilant filled the role of a light patrol cruiser, able to go on extended cruises on the edge of Federation territories. It was lightly armed and did not rely on consumable munitions.
It did not take long, however, for the true troubles of the design to come to light. The U.S.S. Vigilant on her shakedown cruise encountered several structural integrity field problems, including one accident in which four crewmen were killed when the field in their section 'hiccuped.' Review of the accident found the cause of the accident to be due to a faulty plasma coupling. The entire project was re-evaluated at that point with all active ships being recalled and all new construction halted.
The Starfleet admiralty was dumbfounded. Out of the half a dozen similar design projects that had been contracted out similarly bizarre production or service problems were being encountered. At first they raised the question of possible industrial espionage or some form of sabotage, but this could never be proved.
The few Vigilant Light Cruisers that were still under construction were finished, and the small cadre were entered back into service once Starfleet engineers had certified that all known design flaws had been corrected. From 2300-2341 the ships served in their intended role as a light cruiser. Most of the surviving ships were phased out of active service by the fall of 2341, with two of them reserved for Starfleet Academy use and another for local sector defense on the far side of the Federation. The rest were either mothballed or scrapped, including the U.S.S. Vigilant herself.
One of the Vigilant Light Cruisers assigned to Starfleet Academy was later seized by Admiral Hanson for use as part of the armada to counter the first Borg incursion into Federation space. This ship was lost with all hands at Wolf 359.
Of the other two Vigilants, one remains in Academy service while the other broke down in the mid 2350's and was relocated to the Qualor II surplus depot.