3 Nephi 4:21

And the Nephites were continually marching out by day and by night, and falling upon their armies, and cutting them off by thousands and by tens of thousands.

The Nephites kept marching out day and night. They attacked the robber armies. They killed them by the thousands.

Meanwhile, the Nephites kept marching out day and night, attacking the robber camps and cutting them down by the thousands—by the tens of thousands.