The Second Battle of Chin’toka, 2375

The deadliest battle of the entire Dominion War was one of the most humbling in Starfleet history. No less than 311 of the 312 rallied ships attempting to hold onto the Chin’toka system—the Federation and its allies’ largest foothold into occupied Dominion territory—after the Dominion launched a new counterattack were destroyed during the engagement, due to the use of a surprise new weapon developed by the Breen Confederacy capable of completely disabling a starship’s systems and defenses, including the first USS Defiant.
Although the Dominion spared the escaping survivors as they fled their vessels in escape pods, the loss was so devastating to Starfleet that almost all military operations during the war were halted for a month, as engineers scrambled to counteract the threat of the Breen’s new weaponry.