3 Nephi 4:5

And it came to pass that in the nineteenth year, Giddianhi found that it was expedient that he should go up to battle against the Nephites, for there was no way that they could subsist, save it were to plunder, and rob, and murder.

In the nineteenth year, Giddianhi saw that he needed to go fight the Nephites. His people could not survive without stealing, robbing, and killing.

In the nineteenth year, Giddianhi realized he had to attack the Nephites. There was no other way for his people to survive—they had to plunder, rob, and kill.