Coriantumr does the unexpected; he makes a rapid strike into Zarahemla. Mormon does not record his route, but the most direct would have taken him past the typical Manti defenses. His speed was probably the most important element in this bold move, which also suggests that he must have taken the most direct route, simply bypassing Manti and the other defensive cities of Antiparah, Cumeni, and Judea (Alma 57:1–11) and driving straight for Zarahemla.
This move was daring and dangerous because it put a Nephite army at his back. Had he failed at Zarahemla, Coriantumr’s force would have been in dire straits, with no fortified refuge city available to them, and the Nephite army bearing down from the rear. As it was, Zarahemla’s weakened state made it vulnerable, and Coriantumr’s possession of it gave him both the city’s provisions and a strong defensive position against the Nephite counter-attack. In addition, the loss of the central city and the chief judge’s death would have severely disrupted the government, creating disorder among the Nephites, and perhaps delaying the arrival of any assistance. The loss of the central government would likely lead each city that had been dependent upon Zarahemla to rely upon its own leaders, but without a mechanism for unified action.
Verse 19 specifies that Zarahemla had no time to assemble its armies. Naturally, Zarahemla would have had its own local militia, but most of its army—the soldiers mobilized especially for this war—had been sent to guard the periphery. The bulk of Mesoamerican armies, and certainly that of Zarahemla, was made up of citizen-soldiers who left their everyday occupations to respond to the call to arms. Since Coriantumr’s attack was so rapid, there had been no time to assemble the farmers from the land of Zarahemla (fields, outlying villages, etc.) and therefore Coriantumr not only faced a reduced number of defenders, but the best-trained Nephite forces were also far from his location, a double advantage.