When Ken Burns’ “Civil War” documentary aired in the fall of 1990, viewers were most taken with its readings of letters from fallen soldiers. These simple missives often spoke more about love, family and home than battlefield conditions. Times and wars may change, but the poignancy of letters from the front remain uniquely powerful.

“Last Letters Home: Voices of American Troops From the Battlefields of Iraq” (8 p.m., HBO) visits 10 families who share the final letters and e-mails from loved ones lost to combat in Iraq. Mothers, sisters, girlfriends and fathers face the camera and invariably find their voices choked with emotion as they recite passages.

The correspondences share feelings of boredom and worry and of the slow passage of time in a hostile land. But they are also filled with concern for their families and friends back home.

• “ER” (9 p.m., NBC) returns to form with a powerful special episode starring Ray Liotta. Shot in real time, “ER” follows a single patient, Charlie Metcalf (Liotta), a hardened alcoholic ex-convict who shows up in the waiting room complaining of pains and delusions and ends up surrounded by a medical team fighting to save his life. Along the way, Metcalf slips into hallucinations and dreams that fill out the details of his broken life, showing us how he hit the bottle and the skids after a single traumatic event.

Tonight’s other highlights

• Bad feelings between the men and women on “Survivor” (7 p.m., CBS).
• Seth and Ryan re-matriculate on “The O.C.” (7 p.m., Fox).
• Tom Hanks stars in the realistic 1998 war drama “Saving Private Ryan” (7 p.m., ABC), directed by Steven Spielberg.