The phased polaron beam is a type of directed-energy weapon that fires a beam of polarons at the target. The beam is immensely powerful, and at first had a devastating effect on Federation shields, though eventually this setback was overcome. (DS9: "The Jem'Hadar"), (DS9: "The Die is Cast") However, it seems that the Romulan and Cardassian ships did not have these modifications. The Phased Polaron Beam is used in Dominion warships and sidearms.
In 2372, while on a diplomatic mission to negotiate a trade agreement between the Karemma and the Ferengi, the Defiant was attacked, and repelled enemy fire. (DS9: "Starship Down") The Dominion did not become aware of the shield modifications until the Second Battle of Deep Space Nine in 2373, when Dominion officers were surprised to see Deep Space 9's shields holding. (DS9: "Call to Arms").
Jem'Hadar polaron rifles include an anticoagulant in the energy stream. This prevents any non-fatal rifle wounds from healing, forcing the enemy to devote resources into caring for them. (DS9: "The Ship", "Change of Heart") These weapons were replaced by plasma rifles in late 2375. (DS9: "Tacking Into the Wind")