second season, JAG moved from NBC to CBS. Bellisario had previously received offers from CBS and ABC to pick up the series, which was reworked to be one of both "legal [drama] and action". Following the departure of series co-star Tracey Needham and also the unavailability of Andrea Parker, who was the female lead in the pilot episode and who had had guest appearances in the first season as Caitlin Pike, due to her starring role on The Pretender, meant that Bellisario had to create a new female lead for the next season. Catherine Bell made her first appearance in JAG during the season 1 finale playing another character which was killed off in that episode. "It was a really important character for Don Bellisario, who created the show, because Harm was in love with this woman," she said. Bell explained: "I went after the role ... after I had read the breakdown for Mac and they brought me in." The breakdown for Mac was that she would have to be "5′9″ or taller, brown hair, tough and feisty, martial arts experience a plus—that was me," Bell then wrote Bellisario a letter telling him how she "was perfect for Mac, and wouldn’t it be interesting if his new partner looks like the dead love of his life..." "Six callbacks later, I got the role" and "When I finally got the part, Don thanked me for being persistent enough to write the letter." Executive Producer/showrunner Donald P. Bellisario and CBS President Les Moonves "cast Catherine Bell, and [Bellisario] never heard another word from [Moonves] - who took great delight in the fact that it was part of the building block that started the CBS turnaround". To prepare herself for taking on the role of playing a commissioned officer in the Marine Corps and a judge advocate on network television, "I knew a bit about the Navy before I began the role, but I knew nothing about the Marines," Bell spent time doing research at Camp Pendelton, the principal US Marine Corps base on the West Coast, located between Los Angeles and San Diego, "I met and talked to 20 female Marine officers and got to see what they go through and learn how they feel about the Marines. There's a real sense of honor and integrity among the Marines and I got a real sense of that while I was there.