Prince Andrew returned from the Falklands War "a changed man", he said in a now deleted piece posted on his ex-wife's Instagram account.
The Duke of York recalled his time as a helicopter pilot in the conflict 40 years ago in three posts on Saturday.
His piece was initially signed off as HRH The Duke of York, before the reference to His Royal Highness was soon removed.
And only hours later all the posts were removed.
It is unclear why the 700-word account was taken down.
But Andrew gave up the right to use HRH in an official capacity in January when the
Queen stripped her son of his honorary military roles as he faced a US civil action over sexual assault allegations, which he denied.
Virginia Giuffre sued Andrew for allegedly sexually assaulting her on three occasions when she was 17. The case later reached a multi-million pound settlement out of court.
In the first Instagram post, Sarah, Duchess of York wrote that she had asked Andrew for his reflections on the 40th anniversary of his sailing from Portsmouth to the Falklands.
Prince Andrew began: "As I sit here at my desk on this cold crisp spring morning thinking back to April 1982 I've tried to think what was going through my mind as we sailed out of Portsmouth lining the flight deck of HMS INVINCIBLE."
He concludes: "So whilst I think back to a day when a young man went to war, full of bravado, I returned a changed man.
"I put away childish things and false bravado and returned a man full in the knowledge of human frailty and suffering."
The 62-year-old said he was thinking about those experiencing conflict today.