Here the word-final ps of camps is extant in 𝓞, so all the early textual evidence supports the plural camps in this passage. The 1874 RLDS edition replaced the plural camps with the singular camp, and this reading has been retained in the RLDS text. Modern English readers expect the singular noun here. And usually the Book of Mormon text uses the singular (20 times), including one example in the preceding verse:
It may have been this instance of the singular camp that prompted the 1874 change in verse 13 of camps to camp—and perhaps also prevented the editors for the 1908 edition from restoring camps in verse 13, even though camps is the reading in 𝓟. Yet despite these 20 examples of camp, there are several other examples where the text has the plural camps:
So either reading is theoretically possible in Alma 47:13. We therefore follow the earliest textual sources and maintain the plural camps .
Summary: Maintain the unexpected but original plural camps in Alma 47:13: “and surround those men in their camps”; such usage is found later on in the text (in Mormon and Ether).