They participated in a war against their enemy, the Kradin, in 2374. They were known to conscript new soldiers to fight for their cause through the extensive use of propaganda, psychotropic manipulation, and brainwashing. Commander Chakotay was a victim of those techniques after he was captured following the loss of his shuttlecraft.
There were several small contingents. After Chakotay had been captured by the Vori, he was brainwashed and subsequently "rescued" by members of the Fourth Defense Contingent. Later, when Chakotay walked into Larhana settlement, he met Karya, whose brother Daryo was team leader of the Seventh Defense Contingent, which contained around twenty men. (VOY: "Nemesis")