There was a brief period during WWII when a great deal hinged on one woman's grief for her dog. The woman was Nathalie Sergueiew, a Russian whose family had fled to France in 1917 to escape the Revolution. In 1939 she began working for German intelligence - and very shortly thereafter became a double-agent for the Allies, codenamed "Treasure" by the British.
She had had to leave her dog Frisson behind in her Madrid posting, with a boyfriend's promise that Frisson would be smuggled into Britain. But the boyfriend failed, and Frisson died (I haven't found out how). In misplaced revenge, "Treasure" threatened to slip a code into her transmissions to Germany that would tell them she was being held against her wishes. If she had, more likely than not the Allies' entire double-cross system would have come crashing down.
Luckily, she didn't. She went back to France, and eventually wrote a tell-all memoir that was published in 1968. You can read more about "Treasure" here, and learn more of the spying details here - no mention of Frisson, but there is a photo of Sergueiew.