How about both nations? Japan attempted to invade Korea in the late 1500s, and China (under the Ming Dynasty) intervened.

/u/Nelson_Mac says it pretty well here

In 1593, one year after the war started, Hideyoshi's generals and the Ming generals agreed to a ceasefire in Korea. To get this ceasefire to become permanent, generals from both sides forged letters to Hideyoshi and the Ming emperor.

The Ming generals sent envoys to Hideyoshi who pretended to be imperial envoys from the Ming emperor and Hideyoshi's generals lied to Hideyoshi saying that they were apologizing.

Hideyoshi in turn sent an official letter demanding a bunch of things. He wanted the southern 4 provinces of Korea and the Ming emperor's daughter (to be the wife of the Japanese emperor).

Of course the Ming generals disagreed and demanded that Hideyoshi surrender. So Hideyoshi's generals rewrote the letter in Korea saying he surrendered and sent their own envoy onward to Beijing.

Needless to say this kind of lying to both sides would not have positive results. Hideyoshi thought that he won, the Ming court thought that they won...

In 1596 when the Ming court sent their real envoy to Japan, Hideyoshi found out that his demands were completely ignored and ordered a renewal of hostilities. And so the second invasion started in 1597. (This war was a mess to start with but this botched negotiation has to be one of the worst in diplomatic history as well.)

Ming general Shen Weijing was executed by the Ming court for lying. Meanwhile among Hideyoshi's generals, the forgers (Ishida Mitsunari and Konishi Yukinaga) schemed to get the hardliner (Kato Kiyomasa) under house arrest. Kato was released once the forgery was discovered. (But Ishida and Konishi were not punished for it.)

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