Gul Dolak is the Cardassian warship commander who demands that the Enterprise-D abandon a Bajoran vessel it is escorting, and then destroys it, in the fifth-season episode Ensign Ro.
Gul Dolak appears in Ensign Ro. After Jean-Luc Picard finds the Bajoran resistance leader Orta and arranges to escort him and his people to a resettlement camp, Dolak's warship crosses the border and confronts the Enterprise.
Dolak insists that the small Bajoran ship is carrying terrorists responsible for an attack on a Federation colony and demands that Picard withdraw. Admiral Kennelly, who has been secretly dealing with the Cardassians, orders Picard to comply.
Picard does pull back, and Dolak blows the ship apart, but it was empty and flown by remote control. The trap exposes the truth: the Cardassians staged the colony attack themselves to trick Starfleet into delivering Orta to them.