This verse is deceptively simple. Noah sends armies. They are victorious. They return "rejoicing in their spoil." From such simple descriptions we must glean possible history.
Remember that the incursions against Noah's people were small, probably perpetrating by marauding bands for the purpose of gaining food (which is about all they were going to get by attacking people in their fields…"riches" wouldn't be handy as they were working). Noah's reaction against these small bands is to send "armies." Numerically there is a huge difference between a small band and a single "army," let alone "armies."
Secondly, just as with Zeniff, the armies are sent out against "Lamanites." The changes of finding the precise Lamanites is extremely slim. In fact, if the marauders were out for food, they might even be marginal to main Lamanite society. Nevertheless, Noah's armies do find people to drive back, just as Zeniff's did. Just as with Zeniff's event, it is quite possible that the attacks were justified against Lamanites, but ended up against hamlets rather than against those specific bands responsible for the thefts.
Lastly, the armies return with "spoil." They don't "come home with that which was stolen." They come home with "spoil." This is the benefit (at least the ancient economic benefit) of war. When a people is conquered, their goods are forfeit. Thus Noah avenges attacks on food sources with attacks on unspecified targets from whom "spoils" are taken.
From the official position of the Lamanites, it would be quite understandable that the tensions between the Lamanites and Noahites escalate. The politically complex Lamanites would be extending protection to hamlets, but probably saw the marauders as bandits not supported by the Lamanites (just as was suggested for Zeniff's case). The reprisal against protected peoples when the perpetrators were seen as outlaws would justify the Lamanite response. While there is no direct evidence to suggest that the Lamanites really were responding to these conditions, this is one way to view the evidence, and the alternative simple sees the Lamanites as perpetrating wars because they were "bad." I suggest that explanation is too simplistic.