First appearance of the green shirt Captain Kirk wore in the original series.
During the conversation in the field hospital tent between Kirk and Billy, the background music is the 18th century song "Charlie is Our Darling." This song was sung, with different words, by Uhura in the TOS episode "Charlie X" Charlie X (1966).
There is a Wilhelm scream at 23:42, during the battle when a Union soldier is shot.
While speaking to the soldiers around the campfire in 1862, Kirk says "What we say here will soon be forgotten, but what you do here will be remembered." Kirk is paraphrasing part of the Gettysburg Address delivered by President Lincoln in 1863: "The world will little note, nor long remember what we say here, but it can never forget what they did here."
Opening text: Dedicated to the lovely and enduring spirit of our dear Grace Lee Whitney