He said this specific phrase: "Centuries ago, disastrous first contact with the Klingon Empire led to decades of war."
Picard is as multi-cultural as you can get, likely he was referring to one of the Federation races who did in fact experience "decades of war" following their first contact with the Klingons.
The Romulans talk about conquest and numerous wars/campaigns fought in BoT
Spock: The Neutral Zone established by treaty after the Earth-Romulan conflict a
century ago ... The treaty has been
unbroken since that time.
Commander: Danger and I are old companions.
Centurion: We've seen a
hundred campaigns together, and still I do not understand you.
Commander: Our gift to the homeland,
another war.
Centurion: If we are the strong, isn't this the signal for war?
If the RNZ hadn't been violated in a century, just who the hell were the Romulans fighting? A military campaign is a term used for a large scale, long duration, significant military event, but not necessarily a war in of itself. An example would be the Pacific campaign during WWII. If the Commander is strictly a starship commander, then the Romulans were fight people with at least space fight capacity, perhaps even a warp driven culture.
The trick of taking his ship through a comet's tail to lead an opponent into an inferior tactical position might have been one the Commander used repeatedly before with different foes, in multiple wars.





