"I saw more death than you but I won my battles and deserved this command. I deserved it!"
- – Colonel Ari Ben Zayn to Commander Sinclair, 2258
A seasoned combat veteran, Ari Ben Zayn's career included deployments in Israel, on New Jerusalem and Cyrus III. When funding for the fifth Babylon Station was approved in 2255, Ben Zayn was considered to be one of the front-runners among the candidates for the station commander's post. However, as the Minbari Federation – who were contributing a significant portion of the funds to build the station – rejected Ben Zayn and a number of other high ranking candidates, insisting that Commander Jeffrey Sinclair was their only preferred choice. Ben Zayn was galled to say the least, believing that he legitimately deserved the post.
In 2258, Ben Zayn got his opportunity to lay claim to Sinclair's job when Bester, a Psi Cop and friend of Ben Zayn, arranged to have him travel to Babylon 5 to investigate the loyalty of the station's command staff, the intent being to remove Sinclair by taking advantage of the new loyalty tests instituted by Vice President Clark. Earlier in the year Bester's partner had been killed on B5 in an incident involving a rogue telepath named Jason Ironheart and the Psi Cop had promised the uncooperative Sinclair that he'd "be seeing" him again. Bester assigned Ben Zayn a Psi Corps liaison—Mr. Harriman Gray—to act as his assistant and perform the loyalty scans.
Ben Zayn left LaGrange Station 2 with Gray in tow, posing as a rep for Quartermaster Corp under the alias "Aaron Franks." Once on the station, Ben Zayn wasted no time in using his cover to try to gauge people's opinion of Sinclair, quickly attracting the suspicions of Security Chief Garibaldi. His cover effectively blown, Ben Zayn identified himself as being an EIA investigator. Shortly thereafter, he began a formal inquiry into all of Sinclair's command decision going all the way back to the Ragesh III incident earlier in the year. The inquiry ultimately failed, after the Colonel tried to relieve Sinclair and assume command of the station himself when Sinclair provoked Ben Zayn into an emotional outburst in Mr. Gray's presence, betraying his unstable mental condition. Turning wild, Ben Zayn struck Gray and accused the command staff of mutiny, forcing Gray to render the Colonel unconscious and effectively ending his "investigation."