Operation Return was the combined Starfleet and Klingon Defense Force assault against the Jem'Hadar and Cardassian military forces in the Bajoran sector, launched in mid-2374. The objective of the mission was the recapture of starbase Deep Space 9, which had been captured by the Dominion in the opening battle of the war approximately five months previously. It is considered one of the more pivotal battles of the Dominion War.
In the opening months of the war the Federation suffered an almost unbroken series of defeats at the hands of the Jem'Hadar, and showed little capability of stopping and turning back the Dominion's all-out offensive. In addition, Starfleet's few attempts to mount counteroffensives, such as the Seventh Fleet's attack on the Tyra system, were met with overwhelming losses. Out of the 112 ships in the Seventh Fleet, only 14 survived the fight at Tyra and made it back to Federation lines. The Federation and her Klingon allies were unquestionably losing the war.