The original manuscript reads “come down to battle”, although only the last two letters of down are extant in 𝓞. There is precisely room in the lacuna for the first two letters of down. In copying to the printer’s manuscript, Oliver Cowdery accidentally omitted the adverb down.
The Lamanite territory is at a higher elevation than the Nephite territory to the north. The Lamanites, when they attack the Nephites, are characteristically referred to as “coming down to battle against the Nephites”:
Thus the use of down in Alma 46:30 is expected.
Summary: In accord with the reading of the original manuscript, restore the adverb down in Alma 46:30 (“and cause them to come down to battle against them”).