Mr. Laser Beam wrote:
Actually it was the reverse. The Dominion declared war against the Federation.
I would argue that the Feds declared war implicitly by mining the wormhole, which was in itself an act of war.
But as for the OP's question, no, the Feds did not formally declare war. They like to do and endorse nefarious things yet without taking upfront responsiblity for them. Conducting war without declaring war is one of those things. The genocide disease is another, etc.
Because we always see the internal machinations of Federation government, and that disease certainly wasn't Section 31's work instead of the UFP. Nope.