How to say "farewell letter" in English?

There's a saying in China that "Hongyan sends love", which means that lovers express their love to each other by writing letters. But if you receive a dear John letter, that's not good. Because in the west, a dear John letter refers to a dear John letter written by lovers to each other.

"Dear John" became a popular word during World War II. Men enlisted in the army, leaving behind their wives or girlfriends. Because they worked hard abroad all the year round, their lovers moved on and found someone else. This kind of dear John letter is usually called dear John letter. The beginning of a letter is usually fixed: "I found my other half, but it's not you." So I think we'd better separate. "

As you can imagine, it is very painful for brave soldiers to receive a dear John letter from a distant lover on the battlefield. What is more painful is that they are all called "dear friends". Because such letters often bring unforgettable sadness to soldiers, "dear John letters" were widely circulated after the war.

Interestingly, the "dear John letter" also led to another sentence, "That's all she wrote". During World War II, a joke was widely circulated in the army: a soldier told his comrades about his girlfriend's future beliefs. "Dear John," he stopped as soon as he spoke. Comrades advised him to continue reading, and he said, "That's all she wrote." That's all she wrote, and I was dumped! )