Alma 49:18

Now behold, the Lamanites could not get into their forts of security, by any other way save by the entrance, because of the highness of the bank which had been thrown up, and the depth of the ditch which had been dug round about, save it were by the entrance.

The Lamanites could not get into the Nephite forts any other way except by the entrance. The dirt bank that had been thrown up was too high. The ditch that had been dug all around was too deep.

The Lamanites couldn’t get into the fortress any way except through the entrance. The earthen walls were too high, and the ditches dug around them were too deep.