What only ended once?

In the beginning scene of the finale this conversation happened:

B: Trying to prove me wrong aren't you?

Jacob: You are wrong.

B: Am I? They come; they fight; they destroy; they corrupt. It always ends the same.

Jacob: It only ends once. Anything that happens before that is just progress.

So what are they referring to when they say "it"?

Could this be the war?

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