Here in the printer’s manuscript, Oliver Cowdery initially wrote their instead of the correct the before weapons, probably under the influence of the prepositional phrase postmodifying weapons, “of their rebellion”. Oliver virtually immediately caught his error here in 𝓟 and crossed out the final ir. Although we cannot be sure that the crossout is Oliver’s, it seems to be; in addition, there is no observable change in the level of ink flow for the crossout. The original manuscript is not extant for the phrase “the weapons of their”, but spacing between extant fragments supports the shorter the weapons rather than the longer their weapons. Further support for “the weapons of their rebellion” comes a few verses later when the text virtually repeats the language of Alma 23:7:
There is considerable evidence in the manuscripts that Oliver Cowdery tended to anticipate a following their and allow it, if only momentarily, to replace a correct the (for a list of examples and some discussion, see under Alma 1:26). We have another example close by where the before weapons was accidentally changed to their; in this case, the error was made in the 1849 LDS edition:
In this instance there was no following their to trigger the change, but there are two surrounding occurrences of they: “they buried ... or they buried”. Moreover, “their weapons of war” is very common in the text (occurring 24 times). In any event, the critical text will restore the the before weapons in both Alma 23:7 and Alma 24:19.
Summary: Maintain in Alma 23:7 the definite article the before weapons, the virtually immediate correction in 𝓟 (here the earliest extant textual source).