Jaro Essa was a male Bajoran who lived during the 24th century. A politician, he rose to the position of minister in the Bajoran Provisional Government, later becoming leader of the Alliance for Global Unity.
In 2370, Jaro became the leader of the Alliance for Global Unity that sought to remove the Federation from the Bajoran system. He attempted to bring down the Provisional Government and install himself as leader of Bajor.
Later that year, Jaro appointed Li Nalas to the post of Bajoran liaison officer on Deep Space 9 with the designation of navarch, following his return from Cardassia IV. He had Kira kidnapped when she came too close to discovering his plot. Jaro revealed to her that he was the leader of the Circle, and that he assigned Li Nalas to the station so the war hero wouldn't interfere with Jaro's coup.
He was buying weapons from the Kressari who were a front for the Cardassians who were trying to undermine the Bajoran government. He believed that if Bajor was heavily armed, it would not need anyone's protection. Bajor could order the Federation out. Jaro was assisted in his dealings by Vedek Winn Adami, General Krim, and Colonel Day. His plan failed when Kira and Jadzia Dax revealed to the Bajoran ministers that the Cardassians were secretly behind the arming of the Circle and provided evidence to prove it. (DS9: "The Homecoming", "The Circle", "The Siege")
"What you did, major, was declare war on Cardassia. Thankfully they declined the invitation."
"I'd do it again if it meant bringing Li Nalas home."
"Yes, I'm sure you would. And though officially I have to warn you that the next time you disobey orders will mean the end of your military career, as a private citizen I want to thank you for what you've done this day."
"Would you mind if I address the crowd? You can't expect a politician to give up an opportunity like this."
"You go right ahead."
"Thank you. Fellow Bajorans, I have only one thing to say to you, to ask you, really. Never forget this moment. Because I promise you one day your children and your grandchildren will ask you what it was like the day Li Nalas returned to Bajor."
"The Navarch has returned to assume his new post. He's been made the Bajoran liaison officer to Deep Space 9."
"I already have a liaison officer."
"Not anymore, you don't. Major Kira is no longer assigned to this post. She's been recalled to Bajor."
"Major Kira has long been an outspoken opponent of the provisional government, of reason, of progress and now finally, of me. I am honored to be included, Major, but I have no intention of allowing you to disrupt the orderly transition of power with these wild charges."
- - Jaro Essa, on being confronted with proof the Cardassians were supplying the Circle (DS9: "The Siege")
Jaro was played by actor Frank Langella.
Langella's costume comprising an asymmetrical mauve jacket with zips and snaps on the right front and sparkle accents within the fabric on the left, in addition to matching pants featuring black elastic stirrups and suspenders, was sold off in the It's A Wrap! sale and auction on eBay for US$370.00. 
Langella chose not to receive on-screen credit for his appearance. As Director Winrich Kolbe explained, "He wanted to do the show. He did it for his children, because they loved the show. It was not done for money or exposure." (Star Trek: Deep Space Nine Companion (p. 78))
Indeed, Kolbe had a lot of respect for Langella as an actor, recalling, "He scared the shit out of me. There's a mythology around him. He's a tremendous actor and he's got those dark brown eyes that seem to strip you bare of anything that you're wearing emotionally or literally. When he popped up on the first bit, and I know exactly what it was (it was the side entrance to the air lock that leads to the cargo bay), we started rehearsing, and I figured, 'This guy could be trouble', because there's something in him that tells you, 'Watch that guy. If you tell him what to do, he might just tell you to fuck off'. But he didn't. He was terrific. We talked about what he wanted to do. We're not talking about any very deep characterization here. There wasn't much there, and I figured whatever he brings to it, unless he's way out of the ballpark, can be handled. He's so good as an actor that you can't go wrong with him. And it was always, 'Would it be alright if I would be on this side?...' His instincts were perfect, and he didn't punch it in. He didn't say, 'I'm going to stop here and I don't care where you wind up with the camera,' which sometimes happens and you have to pedal really fast. He was also very shy. He didn't even want to announce that his last shot was done. He had said, 'Once we shoot the last shot, please don't say, 'This is the last shot for Frank Langella.' He just faded away." (Captains' Logs Supplemental - The Unauthorized Guide to the New Trek Voyages, p.62)
Producer Ira Steven Behr was delighted that Langella was chosen to play Jaro, stating he was, "a lot of fun to write for. Seeing [Louise] Fletcher and Langella together was great." In a 2011 interview with StarTrek.com, Behr recalled that he was "very psyched when Frank Langella came on. I was psyched that we got Frank Langella to do three episodes." (Star Trek: Deep Space Nine Companion (p. 78); )
Similarly, actress Louise Fletcher recalled, "I liked that show very much, and I enjoyed working with Frank Langella. I got a very lovely note from Frank, saying how much he enjoyed working with me." 
Star Trek author Keith R.A. DeCandido thought Langella, "sells Jaro as an understandable (if not sympathetic) character. As Krim says at one point, 'We're all patriots, commander,' and Jaro truly believes he's doing what's best for Bajor. What he doesn't sell, because the script won't let him, is why so clever a character can't see the long-term implications of kicking the Federation out. Even if the Cardassians weren't the ones arming the Circle, their goals still play right into the Cardassians' hands, as tossing Starfleet paves the way for Cardassia to come back and claim the wormhole (which is probably a much bigger prize to them than a planet they already abandoned)." 
In the Star Trek: Terok Nor novels Day of the Vipers and Dawn of the Eagles, Jaro serves as a major in the Bajoran Militia in the year 2318, and is later present for the official first contact between his people and the Cardassians, which eventually leads to the Occupation of Bajor a decade later.
When a group of aliens plan to destroy Bajor in the novel Objective: Bajor, Jaro lends his assistance to Bajoran First Minister Shakaar Edon. This takes place in the year 2372. When Sisko and Shakaar attempt to negotiate with two of the aliens, Jaro threatens to kill them, which leads to his being knocked out by Shakaar.
The Worlds of Star Trek: Deep Space Nine story "Fragments and Omens" reveals Jaro was forced out of office following the events of "The Siege" and imprisoned at Kran-Tobal prison, where he remained until at least 2376.
Jaro's mirror universe counterpart (β) is featured prominently in the novel The Soul Key, set in the year 2377. The novel depicts him as one of the leaders of the Bajoran dissident movement against the Klingon-Cardassian Alliance as well as Winn Adami's husband.