Multiple realities
(covers information from several alternate timelines)
Tarqan was a Romulan who served in the Romulan Star Empire military. He was the uncle of Decius.
Tarqan and the future commander of a Romulan Bird-of-Prey served together in the Reman Campaign. Tarqan perished when their commanding officer forced them to keep fighting after they had lost weapons and the only logical course was retreat.
Decius had believed that Tarqan's death was a "great victory for Romulus". In an alternate 2266 when he participated in a mission to test the Federation's resolve, his commander, Tarqan's former comrade, clarified to him that Tarqan's demise had been an unnecessary one borne out of pride. (SNW: "A Quality of Mercy")