3 Nephi 2:13

And it came to pass that before this thirteenth year had passed away, the Nephites were threatened with utter destruction, because of this war, which had become exceeding sore.

Before this 13th year had passed, the Nephites were in danger of being completely destroyed. This war had become very bad.

Before the thirteenth year ended, the Nephites faced complete destruction. The war had become unbearably brutal.