During the conflict over Ryloth, a planet under siege, Admiral Dao was in charge of a fleet belonging to the Galactic Republic's Open Circle Armada during the battle. This collection of starships was meant to be a supply fleet aiding the people of Ryloth, trying to defend it against the Confederacy of Independent Systems' ground invasion and blockade. Above Ryloth, Dao's fleet was defeated and obliterated by Separatist naval forces, resulting in Dao's death.
At a minimum, Dao's fleet included a pair of Venator-class Star Destroyers; these vessels were annihilated after taking heavy fire from the Separatist ships.