Here we have two cases of variation involving the preposition of. The first case deals with the placement of the preposition in the relative clause “which the Lamanites have obtained possession”. 𝓟 reads without any preposition at all, as do all the printed editions except for the last two LDS editions (1920 and 1981). The 1920 edition added the expected of at the beginning of the relative clause. This relative clause is extant in 𝓞; there is definitely no of before the relative pronoun which, but the of is partially extant at the end of a line in 𝓞. When Oliver Cowdery copied the text from 𝓞 into 𝓟, he apparently skipped the of at the end of the line in 𝓞. For evidence that Oliver sometimes omitted small words at the ends of lines in 𝓞, see the discussion and examples listed under Alma 11:21.
Usage elsewhere in the text supports placing the of at the end of the relative clause. In the Book of Mormon text, whenever the relative clause refers to possessing something, the of is found at the end of the relative clause, not at the beginning:
Thus the critical text will restore the original of at the end of the relative clause here in Alma 56:13: “these are the cities which the Lamanites have obtained possession of ”.
The second case of variation involving of has to do with the mixed gerundive that occurred in the earliest text for this passage. Although 𝓞 is not extant for all of the gerundive, it is suffi- ciently extant to show that there was no of between the gerund shedding and the direct object the blood. Moreover, there is clearly room in the lacuna for the definite article the before shedding. The transcript for 𝓞 reads as follows:
Thus it appears that 𝓞 read “by the shedding the blood of so many of our valiant men”. When Oliver Cowdery copied the text from 𝓞 into 𝓟, he added the preposition of after shedding, thus making the gerundive more nominal in form (“by the shedding of the blood of so many of our valiant men”). Another possibility would have been to omit the the before shedding, which would have produced a more verbal gerundive (“by shedding the blood of so many of our valiant men”). As discussed under 1 Nephi 17:32, the mixed gerundive construction without the of occurred fairly often in the original text of the Book of Mormon (for a complete list of examples, see under gerundives in volume 3). The critical text will restore the original instance of the mixed gerundive here in Alma 56:13.
Summary: Move the preposition of at the beginning of the relative clause in Alma 56:13 to the end of that clause (giving “the cities which the Lamanites have obtained possession of ”); the clause-final position for the of is supported by the reading in 𝓞 as well as by usage elsewhere in the text; also restore the mixed gerundive in this passage: “by the shedding the blood of so many of our valiant men” (also the apparent reading in 𝓞).