We have examined the catalog of weapons of war in an earlier discussion. In this particular verse, the interesting phrase is "…with all manner of weapons which we could invent…" It is doubtful that the "inventing" of weapons really mean the creation of weapons not previously known, but rather the creation of the known weapons. Until this time the Zeniffites appear to have concentrated more on their building and agriculture rather than weapons of war. When this idea of "inventing" weapons is combined with the information in Mosiah 10:1, it is most probable that Zeniff is referring to the rapid creation of weapons with which that particular skirmish could be fought:
Mosiah 10:1
1 And it came to pass that we again began to establish the kingdom and we again began to possess the land in peace. And I caused that there should be weapons of war made of every kind, that thereby I might have weapons for my people against the time the Lamanites should come up again to war against my people.