Captain Moroni's Fortified Cities
I found this youtube video by the National Geografic Society with Dr. Arthur Demarest who was invesigating the manor of fortification of some Mayan cities. He is not a member of the LDS faith as far as I know but the manor of fortification seams to match Captain Moroni's fortification of the Nephite cities as discribed in the 49th chapter of Alma. Although the video talks mostly about 800 AD the manor of fortification is said, in the book of Alma, to have been first used in 72 BC by Captain Moroni. The video is 23 minutes long but around minute 17 things get interesting. Read the verses below and then watch the video from minute 17 and on. The whole video is very good and I suggest watching it in its entirety afterwards.
https://www.youtube.com/watch?v=9KlzzNu3FpQ
Alma 49: 4-8, 21-22
4 But behold, how great was their disappointment; for behold, the Nephites had dug up a aridge of earth round about them, which was so high that the Lamanites could not cast their stones and their arrows at them that they might take effect, neither could they come upon them save it was by their place of bentrance.
5 Now at this time the chief acaptains of the Lamanites were astonished exceedingly, because of the wisdom of the Nephites in preparing their places of security.
6 Now the leaders of the Lamanites had supposed, because of the greatness of their numbers, yea, they supposed that they should be privileged to come upon them as they had hitherto done; yea, and they had also prepared themselves with shields, and withabreastplates; and they had also prepared themselves with garments of skins, yea, very thick garments to cover their nakedness.
7 And being thus prepared they supposed that they should easily overpower and asubject their brethren to the yoke of bondage, or slay and massacre them according to their pleasure.
8 But behold, to their uttermost astonishment, they wereaprepared for them, in a manner which never had been known among the children of Lehi. Now they were prepared for the Lamanites, to battle after the manner of the instructions of Moroni.
...
21 And it came to pass that the captains of the Lamanites brought up their armies before the place of entrance, and began to contend with the Nephites, to get into their place of security; but behold, they were driven back from time to time, insomuch that they were slain with an immense slaughter.
22 Now when they found that they could not obtain power over the Nephites by the pass, they began to dig down their banks of earth that they might obtain a pass to their armies, that they might have an equal chance to fight; but behold, in these attempts they were swept off by the stones and arrows which were thrown at them; and instead of filling up their ditches by pulling down the banks of earth, they were filled up in a measure with their dead and wounded bodies.