Given the task definition and input, reply with output. The answer will be 'yes' if the provided sentence contains an explicit mention that answers the given question. Otherwise, the answer should be 'no'. Instances where the answer is implied from the sentence using "instinct" or "common sense" (as opposed to being written explicitly in the sentence) should be labeled as 'no'.

Sentence: He says that instead of everyone dying , they could keep at least one of their princes alive . 
Question: What was happening before he decided to keep at least one prince alive?

Yes.