[SunkenCiv]

Ashoka spread Buddhism by the sword, which kinda summons up Kevin Kline’s character in “A Fish Called Wanda”.

Buddha died from eating bad mushrooms, but he was also 80 years old and had fasted off an on for decades after he sought enlightenment by abandoning his wife and child.

[Cronos]

Well, ok, I'll agree that there isn't direct way of proving that it was / wasn't spread by the sword, but history books normally indicate the latter

Also, Indian Buddhist i.e. the older Theravada tradition does state that the Buddha did die from eating spoiled meat while checking up on your answer, I find that Mahayana tradition states that he died of eating spoiled mushrooms and another conclusion (more modern) is that he died of old age. Ah, well, since this was 2500 + years ago, any one of these could be true.