Hugh Nibley asserts that Nephi’s reference to a military garrison of “fifty” (1 Nephi 3:31) seems pitifully small for a great city like Jerusalem. It would have been just as easy for the author of 1 Nephi to have said “fifty thousand,” and made it really impressive. Yet even the older brothers, though they wish to emphasize Laban’s great power, mention only fifty, and it is Nephi in answering them who says that the Lord is “mightier than Laban and his fifty,” and adds, “or even than his tens of thousands” (1 Nephi 4:1). As a high military commander Laban would have his tens of thousands in the field, but such an array is of no concern to Laman and Lemuel: it is the “fifty” they must look out for, the regular, permanent garrison of Jerusalem. The number fifty suits perfectly with the Amarna picture where the military forces are always so surprisingly small and a garrison of thirty to eighty men is thought adequate even for big cities. It is strikingly vindicated in a letter of Nebuchadnezzar, Lehi’s contemporary, wherein the great king orders: “As to the fifties who were under your orders, those gone to the rear, or fugitives, return them to the ranks.” Commenting on this, Offord says, “In these days it is interesting to note the indication here, that in the Babylonian army a platoon contained fifty men”; also, we might add, that it was called a ”fifty,“ --hence, ”Laban and his fifty" (1 Nephi 4:1). Of course, companies of fifty are mentioned in the Bible, along with tens and hundreds, etc., but not as garrisons of great cities and not as the standard military unit of this time. [Hugh Nibley, Lehi in the Desert, F.A.R.M.S., pp. 97-98]
Nibley also states that Jerusalem was run by the sarim or “members of the official class; that is, officers acting under the king, as his counselors and rulers. Further, Laban is cut from the same cloth as Jaush, his contemporary and probably his successor as the military governor of the whole region, in control of the defenses along the western frontier of Judah.” [Hugh Nibley, An Approach to the Book of Mormon, p. 80]