The process of setting guards indicates both the necessity of wariness against retaliation, and the relative size of Zeniff’s people at the time. Guards are necessarily of fighting age, and therefore also of an age to work the fields. To set a number of guards around indicates an ability to produce sufficient for the community without the labor of the guards. This excess production is probably what will fuel king Noah’s excesses. The productiveness of the people might see a confirmation in verses 4 and 5 below.
The nature of the guards is probably more a small number of spies than large garrisons. It is not likely that at this point in time Zeniff could have manned multiple outposts with sufficient men to be a deterrent. Rather, the guards functioned more as spies, as confirmed by verse 7.