Star Trek: Enterprise
Being a prequel, Enterprise was expected to explore territory fans would have previously known about. The era depicted in the series was best known, or perhaps only known, for the Romulan War, a conflict previously referenced in the original series episode "Balance of Terror," where it was established that until that point no human, much less Vulcan, had ever seen a Romulan. Which would necessarily make any depiction of this period, involving Romulans, somewhat problematic.
Enterprise initially solved this dilemma in "Minefield," which does in fact feature the eponymous threat, a problem that becomes another spotlight of Malcolm Reed's penchant for pessimism when he becomes pinned by a mine to the hull of the ship. Captain Archer does his best to reassure Reed, but it's a tough sell.
In the first season, there's an even more vivid example of Reed's tendencies as he and Trip are left stranded in space. "Shuttlepod One" was considered one of Enterprise's early highlights. It should be noted that Reed wasn't alone in his apprehensions. Hoshi Sato was similarly skittish. Everyone's nerves were tested to the extreme in the third season, naturally, as they embarked on a mission to prevent the Xindi from destroying Earth. Trip tended to take most of these experiences in stride. He was also one of the few human males to end up pregnant ("Unexpected"), although even he, or his clone, was reluctant to follow Archer's wishes in "Similitude." ("This is a screwed-up situation," are his exact words.)
In the fourth season, Enterprise revisited the Romulans in a three-part episode ("Babel One," "United," and "The Aenar") that demonstrates both military and infiltration tactics as part of their activities during this period. There had been speculation that the fifth season, which never happened, would have involved events more closely related to the Romulan War itself, and there was a movie trilogy developed, unrelated to Enterprise, that would have done the same. The 2009 movie that was released did involve Romulans, but this is likely a coincidence, much as the fact that the last Star Trek movie before it, Nemesis, featured them too.