Curiously, canon still stays so quiet about the Romulan War that we don't even know the dates! It may have happened between the last two ENT episodes, or well after the UFP was founded, or perhaps was something that happened before ENT but wasn't realized to have happened because ships and news were slow as molasses back then.
The only onscreen source that supports the thing that everybody assumes to be true - that the Romulan War took place between 2156 and 2160, involved just Earth and Romulus and not the Federation, and ended with the battle of Cheron - is an essentially illegible bit of computer screen decoration from the parallel universe of "In a Mirror, Darkly". Everything else about the war still comes from "Balance of Terror" and the books.
Timo Saloniemi
The only onscreen source that supports the thing that everybody assumes to be true - that the Romulan War took place between 2156 and 2160, involved just Earth and Romulus and not the Federation, and ended with the battle of Cheron - is an essentially illegible bit of computer screen decoration from the parallel universe of "In a Mirror, Darkly". Everything else about the war still comes from "Balance of Terror" and the books.
Timo Saloniemi