Another theme could be loss. Maybe the letter was written in the wake of losing someone or something important, like a letter written by a person mourning the death of a loved one, sharing memories and the pain of the loss.
One possible theme could be love. The letter might be a love letter expressing deep affection and passion.
A third theme could be adventure. For instance, if it's a letter from an explorer, it would be filled with tales of new places, strange encounters, and the excitement of discovery.
One possible theme could be mystery. If the letter is from an unknown sender or contains cryptic messages, mystery would be a strong theme.
One possible theme could be isolation. Silence often implies being alone or cut off, and in a back story, it might show a character's struggle with feeling isolated from society or their loved ones.
Nostalgia could be a theme. If it's a story looking back at the time when someone was in pampers, it's often about reminiscing and feeling nostalgic for that period of life. Also, growth and development could be themes. The story might show how a person has changed from being a baby in pampers to who they are now.
Another theme could be the loss of innocence. The war would have exposed people to violence and death, and those involved might have lost their naivete. For example, young soldiers going to Vietnam and coming back changed forever. Also, a theme of friendship might be present. Soldiers or civilians might form strong bonds during those difficult times to support each other.
One possible theme could be regression. It might explore the idea of going back to a more innocent or dependent state, like infancy when diapers are used.
A theme of hope might also be present. The writer could be expressing hope for Jordan's future, or for their relationship to continue or improve in some way.
One possible theme could be love and longing. The wife might be expressing her deep love for her husband and how much she misses him in the letter.
One possible theme could be deception. If the letter contains false information or is used to mislead someone, that would be a major theme.
One possible theme could be identity. If Parker has some sort of mark or feature on his back, it might be related to how he sees himself or how others perceive him.
One possible theme could be adventure. Just like the journey 'there and back again', it might involve exciting experiences related to water, like exploring uncharted waterways.