The military alliance of the Federation, the Klingon Empire and later the Romulan Star Empire that fought the Dominion, the Cardassians and the Breen in the Dominion War.
The Federation Alliance is the coalition that opposes the Dominion in the last seasons of Deep Space Nine. It begins when the Klingons restore the Khitomer Accords in By Inferno's Light, and fights from the outbreak of open war in Call to Arms.
For a year the two powers lose ground. The Romulans, neutral under a non-aggression pact, join in In the Pale Moonlight after Sisko and Garak contrive evidence of a Dominion plot against them. The three fleets then take the Chin'toka system in Tears of the Prophets.
The alliance is strained by Breen energy-damping weapons and by Gowron's reckless orders, but holds together. Aided by Damar's Cardassian rebels, it breaks the Dominion lines and forces the surrender signed in What You Leave Behind.