Sixteen years after co-creator Donald P. Bellisario left NCIS, the show's co-creators, producers, and director spoke about the conflict that led him to leave the show. Having begun in 2003, NCIS is a police procedural revolving around the Naval Criminal Investigative Service. It was originally a spin-off of JAG before becoming successful enough to secure spin-offs of its own in NCIS: Los Angeles, New Orleans, Hawai'i, and the upcoming Sydney. Harmon starred in the first 19 seasons as agent Leroy Jethro Gibbs.