Nephi is not particularly clear as to the timing of these wars. It almost appears that he is discussing the wars of annihilation that will ultimately destroy the people who carry his name - but the following verse makes it appear that he is referring to some set of wars that will be prior to the coming of the Savior to the New World.
The history of the Book of Mormon allows us to understand that for the Nephites, the prophecy of war was the easiest to fulfil. with times of peace being more unusual than times of conflict.