The original manuscript has encircle twice here in Alma 48:8; but when copying to the printer’s manuscript, Oliver Cowdery accidentally wrote enclose rather than encircle for the first instance. This created the only occurrence of the verb enclose in the entire text. Otherwise, we have only encircle (26 times). The same verb is used both times in Alma 48:8 because the text is simply stating that Moroni’s armies were encircled by their fortifications (in some cases, by banks of earth, and in other cases, by walls of stone).
Oliver Cowdery made the same mistake one other place in the book of Alma, again as he was copying from 𝓞 into 𝓟; in Alma 53:4, Oliver started to write enclosed in 𝓟 but wrote only the first five letters, enclo:
Oliver immediately crossed out the enclo and supralinearly inserted encircled (spelled as incerceled in 𝓟). In this case, 𝓞 is extant for the last part of encircled. Oliver’s spelling for the word encircle varied considerably in 𝓞 and 𝓟; in this instance, he spelled the word in 𝓞 with an extra e before the final led (these four letters, eled, preceded by a hyphen, begin a line of 𝓞). It is obvious that the word in 𝓞 was not enclosed.
Summary: In accord with the reading in 𝓞, restore encircle in Alma 48:8 (“to encircle his armies”); the original Book of Mormon text has no instances of the verb enclose.