In 2375 the Breen joined the Dominion's war against the Federation/Klingon alliance. They brought with them a decisive advantage - a weapon which, with a single hit, could completely disrupt the power systems of any allied Starship. The weapon was first brought into play at the Chin'toka system, where it was used to devastating effect; an entire allied fleet was utterly defeated and destroyed by the Breen.1In the aftermath, it was discovered that a single Klingon vessel had been able to withstand the Breen weapon without ill effect, apparently because of a minor adjustment which had been recently made to the ship. More than a thousand Klingon ships were quickly modified to give them the same resistance, but this still left the Dominion with a 20 to 1 advantage.2
With no time to research the weapon and develop a countermeasure for Federation and Romulan ships, the allies launched a desparate attempt to steal a Jem'Hadar attack ship from Cardassian space. The attempt succeeded3, and the allies were able to resume the battle in full force.4
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