In a prologue taking place in 2001 in San Francisco, George Takei, widely known for playing Mr. Sulu in “Star Trek,” appears as the elder Sammy Kimura reflecting on what happened in his youth when he and his family were interned, The musical soon moves back in time to the fateful 1941.

The score, with music and lyrics by Jay Kuo, calls for strong singing, which is amply supplied by Lea Salonga and Telly Leung, as sister and brother, Kei and Sammy. Integrated with the book by Marc Acito, Kuo and Lorenzo Thione, the songs are very expressive of the trauma that the internment has brought and the various responses.

Differences occur dramatically. Sammy, gung-ho about proving he is a loyal American, tries to enlist as a soldier, but “Japs” are rejected. Later, when the policy changes, he is able to join the army and he goes off to brutal battle in which many of his buddies are killed. Kei has fallen in love with Sammy’s friend, Frankie Suzuki, played with passion by Michael K. Lee, who believes it his duty to resist, and that leaves an angry rift with them on the part of Sammy, who bitterly considers them traitors.

The spectacle of people being ordered from their homes and allowed to take only few belongings is heartbreaking, and the musical explores the pain inflicted and the difficult conditions in the Wyoming camp, where the soldiers in charge are abusive. Hannah, a kind nurse, played engagingly by Katie Rose Clarke, falls in love with Sammy.

“Allegiance” is strikingly mounted under the direction of Stafford Arima, with music supervision, arrangements and orchestrations by Lynne Shankel and choreography by Andrew Palermo. At times the staging is elaborate, as with a battle sequence. The scenic design is by Donyale Werle, with Darrel Maloney having contributed projection design. Many other hands have helped give the production its impressive look in the face of the challenge of having to cover the sweep of family history as well as the trajectory of the war.