The first principle of war identified in this section is Moroni’s knowing that it is easier to keep the city from falling than to retake it (v. 9). One of the reasons this is true is that there is only one battle in defending the city, but if the city is lost there are two battles—the first to lose it and second one to retake it. Therefore, the losses are heavier both in lives and destruction of property. In the battle against evil, the principle is the same. It is easier to prevent sin than it is to repent of sin. Also there is the destruction of character and virtue in yielding to sin. The cause of the fall of the city was wickedness, as recognized by Moroni and the chief captains (vv. 11–12). We prevent wickedness by abstaining “from all appearance of evil” (1 Thessalonians 5:22). Jesus taught us to pray that we not be led away into temptation but “deliver us from evil” (3 Nephi 13:12; Matthew 6:12). Moroni’s anger is vented in the following epistle.