"War Horse" is not a show in which actors sit in their dressing rooms for long stretches, noodling on their laptops and waiting for the next cue. Case in point: Sanjit De Silva, whose main assignment is Lieutenant James Nicholls. That young officer, whose sketchbook tendencies play an essential part in the production, appears in the first act. For the second half, however, De Silva has in many ways an even more involved task. 

"I have five costume changes in the second half," said De Silva the other day, as we sat in his dressing room after a matinee. "I play German soldiers and British soldiers. It's nonstop running." He added: "There's no easy track" -- a track being an actor's role or combination of roles in a show -- "in 'War Horse.'"

De Silva has been with the LCT production since the beginning, first playing Taff ("a Welshman that I loved") and doing puppetry ("a workout") and, since January, portraying Nicholls. "Getting a chance to switch roles," said De Silva, "has been an incredible blessing, and has helped me maintain my love of the play."

In fact, De Silva had understudied both Nicholls and Captain Charles Stewart in 2011. He went on twice as Nicholls but never got a chance to do Stewart. Not that he didn't get close. After Brian Lee Huynh injured himself in a bike accident, De Silva got a summons to play the Captain. "We had a fight call before the performance," he recounted. "I was on the horse. As I got off the horse, my foot got caught and the horse started to fall toward me. Everybody thought I had broken my leg, but the kind of boots we wear saved me." De Silva had pulled his calf muscle, and returned after missing three shows. The actor finished off the anecdote with the wink that any of us connected to this show must imply when reaching for an equine metaphor. "You gotta get back on the horse."

Of all the twists and turns connected with performing "War Horse," perhaps none has been more significant for De Silva than the simple fact of being cast in the production itself. "I didn't think a brown guy like me could do Broadway," he said. "I've done my share of TV and movies, and I'm usually cast as the South Asian guy. Casting tends to be a lot more literal than in the theater."

De Silva was born in Sri Lanka. He left when he was seven, and he lived briefly in Uganda, Kenya, and the Queens borough of New York City before his family settled in Connecticut, where he attended prep school. At Washington University, in St. Louis, De Silva majored in biology and performing arts. He returned to New York, where he worked as a production assistant for Spike Lee's company, back before the director moved on up to the Upper East Side and left behind Fort Greene, Brooklyn -- where De Silva, it happens, has himself long lived. 

"Eventually," De Silva said, "I realized that I was on the wrong side of the camera. I missed acting." He performed in what he calls "some bad off off off Broadway" and ended up at the Shakespeare Lab at the Public Theater. An acting MFA at New York University followed. 

Late in our conversation, I posed to De Silva the question I pose to all "War Horse" actors who have been with the LCT production lo these 19 months: "How do you keep yourself focused day in, day out?" 

"As I've said," De Silva answered, "changing roles made my work more interesting. But something does seep in after a long time that you have to watch out for. It's easy to get comfortable. You have to keep checking in with yourself. The challenge of a long run is to keep finding new things within the parameters of the show." He added, understandably for someone whose life includes not just "War Horse" but a five-year-old son, "On days when I am tired I wonder how well I'm going to get through the show. But on tired days I sometimes have better shows."

Part of the reason, he suggested, is nerves. "Deb Hecht, one of my teachers at NYU, once told us about a study done on actors. It concluded that the level of adrenaline many actors experience just before they go onstage is similar to that of football players about to take the field for the Super Bowl. So I guess it's no surprise how often that, even on tired days, just as I'm about to step onstage something hits me. Bam!"

Brendan Lemon is the American theater critic for the Financial Times and the editor of lemonwade.com.