"Don't trust them. Don't go back. Kill Peeta. Do what you came to do."
-Boggs saying his last words to Katniss
Joseph Boggs was one of the military advisors of Alma Coin. He was in The Second Rebellion and led The 76th Hunger Games (The name provided to the mission of the rebels going to the Capitol).
Mockingjay[]
Boggs becomes Katniss' personal bodyguard. While in District 8, as the bombs are being dropped to kill some of the rebels there, he covers Katniss with his own body so that she will live, demonstrating his willingness to die for the Mockingjay. After proving that he is not utterly devoted to Coin but the cause itself, he begins to get Katniss' respect and trust. When Coin sends Peeta to join Star Squad arguably in the hopes that he will kill Katniss, Boggs swears that he will keep her safe. He has a heated conversation with President Coin on the subject but is overruled.
This is a major turning point in "Mockingjay" as this conversation between Boggs and Coin shows how far Coin is willing to go in the plan to conquer by any means and ways possible, including killing the Mockingjay. From this arguement it can be assumed that Coin's master plan included the Star Squad being killed in battle. This would not only eliminate her perceived threat from the most popular capable victors and their future influence among the new Panem but also Boggs who may know more about Coin and her dire capabilities and weakness then anyone else has in the series that we known of. Also, Boggs is actually viewed in propos making him publicly recognizable through the districts and Capitol making him justifiably just as influential in being a future leader as even Coin herself.
Boggs was working as President Coin's second in command and was like a puppet to her, as Katniss notes. When Katniss fled the room because of Peeta's interview, Boggs tried to stop her but Gale got in his way and stomped on his face, breaking his nose. Boggs was assigned to guard Katniss while she is in films in the propaganda. Boggs and the group go to District 8 for their first shoot.
When they arrive at District 8, they go to one of the hospitals and decide to comfort some of the patients. Boggs keeps a close eye on Katniss and makes sure nothing happens to her, since he is after all her bodyguard. After their run-in with Finnick, Katniss decides to like Boggs. When the Capitol attacks the hospital, Boggs is ready to go into combat, but holds back Plutarch so Katniss can fight their enemies. Boggs makes sure they are filming as they battle and watches Katniss to make sure she is safe, so they an influence more people to join their side on the rebellion. When the attack is over and Katniss makes a brief speech, Boggs tells them that they have finished filming the propo and they return to District 13 to receive medical treatment. The group meets in the command room and discusses the complete propo. After they finish, they decide to allow Katniss go back in combat and shoot more propos when she has fully recovered. Boggs talks with the head of the rebellion to discuss more topics and objectives they must deal with.
Boggs assists the head of the rebellion in evacuating the entire district to safe bunkers after Peeta warns them of the bombing that the the Capitol would bring on District 13. Boggs, Katniss, Gale and the others resurface to the heavy damaged remains to shoot more propagandas but Katniss and Finnick break down because they cannot take it anymore.
Boggs and President Coin form a rescue team that he will lead to save Peeta, Johanna, Enobaria, and Annie from the Capitol when they were captured as hostages (except for Enobaria since she wasn't seen as a threat) in 75 ADD. Boggs knocks Peeta out after he tried to strangle Katniss. He goes with them to District 2 and enters The Nut with them to meet Lyme. The group argue over the idea of bombing The Nut while it was filled with people. Boggs gives them the choice of blowing them up or giving them a chance of escape. He also updates them of Peeta's condition after they retreat to the Justice Building.
Boggs goes with the sharpshooters squad to the Capitol and is leader of the group. The group train and film more propaganda. When Leeg 2 dies, Peeta is sent as a replacement. Katniss speaks with him about the replacement and Boggs points out Katniss will be a big vote for who will be the new leader of Panem. He and 13 others formed the troop that reached the Capitol and tried to survive it's traps made by the Gamemakers. Sadly, Boggs was the first one to die, in an explosive pod blowing up his legs, eventually killing him. His second in command, Jackson Forbes took over the mission after that. This means that he placed 14/14th place.