The Defiant is hit with a Breen energy dampening weapon and loses power
The result of the Second Battle of Chin'toka
The Second Battle of Chin'toka marked the entry of the Breen Confederacy into the Dominion War in late 2375, in an attack against the Chin'toka system, a territory of the Cardassian Union held by the forces of the United Federation of Planets, the Klingon Empire, and the Romulan Star Empire. The battle was a major defeat for the allies thanks to the use of the devastating and previously-unknown Breen energy dampening weapon.
With the Dominion facing the prospects of a long war and their Founders suffering the effects of a morphogenic virus, they sought additional allies to bring the war to a quick end. After initial contact, the isolationist Breen Confederacy eagerly joined the Dominion.
Within days, the Breen launched a massive offensive against the Federation territories. Most damaging in terms of destruction and morale was a bold attack against Starfleet Headquarters on Earth - the first time open combat had taken place on Earth in over 200 years.
In their initial assault on the allied positions in the Chin'toka system, the Dominion broke through the lines in two places. Starfleet rallied for a counterattack with a force of 312 ships under the command of General Martok.
The Allied fleet opened fire as soon as they were in weapons range. The Breen warships took heavy damage and several were destroyed, but they held long enough to launch their new energy dissipaters. Inexplicably, nearly every allied ship was engulfed in a massive energy-draining field, drifting on emergency power only.
Adrift without weapons or shields, the Allied fleet became easy targets for destruction by the Dominion. Ship after ship was destroyed. The Defiant was among the three hundred and eleven ships destroyed. The only surviving ship was a Klingon Bird of Prey, whose engineer had made modifications to the warp drive that saved the ship. Few ships, including the USS Defiant, were able to launch escape pods. These pods carried scared officers with depleted morale.
An allied reserve force on the edge of the system picked up the escape pods and quickly retreated to Federation-held space.