These Galaxy units were responsible for engaging the larger targets in the combined Cardassian and Dominion fleet.
After several waves of attack fighters opened a hole in the Cardassian front lines, it was observed that several Galor-classdestroyers were positioned in such a way that any vessel that would go through the hole would be trapped.
Viewing this potential trap as perhaps being the only opportunity to break open the Dominion fleet, Sisko ordered Galaxy Wing 9-1 and Galaxy Wing 9-3 to engage the Galor-class destroyers, and effectively "hold the hole open" while all remaining ships headed through.
Sisko attempted to compensate by requesting the Sixth, Seventh, and Eighth Fighter squadrons to regroup and offer their support, but the Dominion had jammed their communications signal by generating a rotating E-M pulse. (DS9: "Sacrifice of Angels")
Analysis of the battle from "Sacrifice of Angels" showed no less than ten Galaxy-class vessels in the combined Federation fleet during Operation Return. This would indicate that there were more than the initial six Galaxy-class starships referenced in the Star Trek: The Next Generation Technical Manual. The total of six ships stemmed from Roddenberry's assumption that Starfleet would not have constructed vessels of that large a size in substantial numbers. The Manual however also stated that an additional six spaceframes were constructed and laid up to be completed at a moment when circumstances so dictated. It can be conjectured that those circumstances arose after the first Borg incursion and that by the time the Dominion War began, all the remaining original Galaxies were operational. It could be theorized that a "Galaxy wing" would be much like modern battle groups with lighter frigates/ships screening the main capital ship(s) (which would make sense due to the size and firepower of a Galaxy-class starship).