A systematic program to place entity claims in tier-1 and tier-2 sources, building the multi-source validation that AI systems require before citation. Corroboration campaigns are not ‘content marketing’ — they are infrastructure construction targeting specific sources that contribute to entity confidence. Each campaign has a defined claim target (which attribute to corroborate), a source tier target (which tier-1/2 sources to pursue), and a measurement protocol (quarterly tracking of whether the claim is now cited). Corroboration campaigns are the primary tactical mechanism for moving from contested to defended posture.