What is a final demand that if not met will end negotiations and lead to a war

 an ULTIMATUM

Explanation:

The term "ultimatum" comes from the Latin verb ultimare, which means "to come to an end."  When someone issues an ultimatum, it means that it is the last action, the final demand.  If the desired response to the ultimatum is not achieved, then punishment will follow.  In your household, this might mean your parent would say something like, "If you don't get your homework done by 7pm, you are not allowed to go out tonight."   When an ultimatum is issued between countries, it will be a demand that must be met or war will be declared.

A famous example of such an ultimatum occurred after Franz Ferdinand, the archduke of Austria, was assassinated along with his wife in Serbia.  On July 23, 1914 (about a month after the assassination), the government of Austria-Hungary issued an ultimatum to Serbia.  The ultimatum demanded that Serbia would ...

The government of Austria-Hungary demanded an answer from Serbia's government within 48 hours, or war would happen.  And war did happen -- a conflict that ended up involving many other countries, which we now call World War I.

d

explanation:

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