Olivier Mira Armstrong

Major General Olivier Mira Armstrong (オリヴィエ・ミラ・アームストロング, Orivie Mira Āmusutorongu) is Alex Louis Armstrong's older sister and the primary heir to the illustrious Armstrong Family. She is in charge of keeping peace on the northern borders of Amestris from her domain, the Briggs Fortress.

Personality
Olivier is a dauntless woman who scoffs at the concept of "equivalent exchange" and believes "survival of the fittest" is the only law in life. Her subordinates are incredibly loyal to her; however, if their attachment to her were to ever put Briggs at any open risk, they are instructed to leave their leader behind. She despises Colonel Roy Mustang and is brutal towards her little brother, considering them both to be weak and insulting to the state military. She is absolutely without mercy to those who she considers to be enemies, but as can be seen in her decision to spare Scar, this is not an absolute rule. Perhaps her closest subordinate and friend is Major Miles, a man of mixed blood with great appreciation towards the General.

The Northern Wall of Briggs
Olivier is first introduced when Edward and Alphonse are sent north with a letter of introduction from Alex to see his older sister. Once in the frigid, snowy plains of the Briggs Mountain range, they are attacked by Buccaneer (believing them to be Drachman spies), and taken before the General herself. Olivier is quick to dismiss her brother's letter and informs the two brothers that she only judges people with her own eyes.

When the Homunculus Sloth accidentally infiltrates the fortress, Olivier uses this opportunity to test the Elrics' loyalty. Mounting a Briggs Tank, General Armstrong leads the defense against the intruding Homunculus, eventually freezing him solid with the harsh weather of the region to her advantage. Now working more closely with the Elrics -- who she suspects might still be withholding information from her -- Olivier is informed of the Nationwide Transmutation Circle, and Central's sinister plans which also seem to threaten her northern soldiers. Fortunately, with the unexpected arrival of General Raven from Central High Command, Olivier decides to prod in deeper into the military's true intentions. Raven, taking the bait, attempts to seduce Armstrong with promises of an "immortal legion" at her command if only she pledged full allegiance to Central.

Infiltration of Central Command
With her true target now made clear and a determination to save her base and soldiers by her own hand, Olivier kills the corrupt General (who had also ordered her to set Sloth free earlier), and answers Führer King Bradley's personal summon. Once in Central City, she confronts him about his true nature and for her boldness is given Raven's seat at Central Command. Working as a sort of double-agent, Armstrong acts the part of ruthless leader if only to obtain the finer secrets of the military for her advantage. In time she is shown the "immortal" lesser Homunculi army by General Gardner and even comes face-to-face with Father himself.

Back at the Armstrong mansion, Olivier asks Philip Gargantos Armstrong to immediately retire and go on an extended vacation, and after defeating Alex Louis Armstrong in an inheritance brawl, she receives the estate. Alex then ask Olivier if she sent their family away from Amestris so they couldn't be made hostages because of the upcoming dangers, instead of giving a respond Olivier just smiles and tells Alex to go away. While visiting to congratulate her, Roy Mustang jokingly comments on the large space of the house and how it could easily fit a battalion inside -- a hidden tip she takes as the Briggs forces covertly move into the large mansion in preparation for the inevitable coming conflict.

The Promised Day
When Mustang begins his attack on the city, Olivier is located in Central Command, where she openly mocks the corrupted Generals and their misplaced sense of security. After shooting down Gardner, she takes on another General as a hostage, a move which ultimately proves useless when Sloth reappears and terminates the General in his attack. Thanking the Homunculus for preventing her from having to "dirty her blade with that scumbag's filthy blood", she fearlessly fights against Sloth and the lesser Homunculi hordes. While slaughtering the immortal soldiers with ease, she finds herself to be less than a match for Sloth and ends up being caught by him after killing him several times. Sloth proceeds to use his superhuman strength to break the General's right arm, but the timely appearance of Alex saves her. While Alex battles Sloth, a squad of Central soldiers comes upon her, and threatens to kill her. However, she simply shouts at them to wake up and look around them. Convincing the soldiers to "Act on their own for once", they aid an injured Alex in the battle against Sloth. After Sloth incidentally re-sets Alex's previously dislocated shoulder, Izumi Curtis and her husband, arrive, and the four of them manage to kill Sloth.

As Father activates the Nationwide Transmutation Circle, Olivier's soul is ripped from her body and she is seen lying on the floor next to her brother. However, she is later brought back to life along with the rest of Amestrians.

After her resurrection, she located Riza Hawkeye and the chimeras, who were watching the battle against Father. When Greed arrived on the scene, he ordered her to remain behind, deeming her too injured to continue fighting. After arguing with him, she reluctantly turned her leader role to her brother. Afterwards, she spotted Bradley's body and realized that Buccaneer had been the one who managed to wear him down enough for Scar to defeat him.

New Beginnings
After Father's final defeat, Olivier has the Briggs forces rescue all those who had been injured in the rubble of the heavily damaged Central Command Headquarters Building, using the opportunity to secretly rescue Scar. When Scar woke up later at a makeshift hospital, Olivier told him that the reason she saved him was for him to work together with Miles to save the Isvalian people and religion (and also to make Roy Mustang get into a bad position once he's found alive). Scar accepted this position, and when Olivier asked him what his real name was, he answered that since he's died twice he does not exist and thus doesn't need a name. He asked to be called whatever she liked.

Olivier Mira Armstrong's final appearance was in the collage of photos at the epilogue, where she is shown annoyed at her brother Alex.

Powers and Abilities
Being the General of Briggs, Olivier has full command of the Fortress. She is very skilled with her family heirloom sword, which she uses unhesitatingly, as well as with firearms, from pistols to rocket-propelled grenade launchers, shooting with deadly accuracy. She is also, like the rest of the Armstrong family, very strong despite her appearance, and is even shown to be stronger than her brother Alex when she effortlessly defeated him while fighting for the head of the Armstrong Family. However, her inability to match Sloth's strength while Alex mean that Olivier merely outmatches Alex in sheer combat prowess, relying more on agility and speed and less on pure strength. Above all she is an excellent leader, not faulting at the suggestion of danger as well as ordering solders who were sent to kill her to work under her.

Trivia

 * Like nearly all military personnel in the Fullmetal Alchemist series, the Armstrong family is named after a military vehicle, vessel or weapon, in this case, the Armstrong Whitworth Whitley (A.W.38 Whitley), a British bomber from early WWII
 * Major General Armstrong's first name, Olivier (オリヴィエ Orivie), is actually a masculine name. It is the French form (pronounced o-lee-VYAY) of Oliver.
 * She has a noticeable hatred to be accused or given anything that is considered feminine, where she will immediately destroy such gift (such as a bouquet that Roy Mustang gave her with flowers that in their name mean feminine). Appearing to hate being called feminine as much as Ed is being called short.
 * Another reason that Oliver destroyed the flowers is because they contained a note from Roy that said "Selim Bradley is a Homunculus."
 * Olivier ranked 8th place in the latest popularity poll, making her the third most popular female of the series (with Winry being second and Riza Hawkeye being first), also making her the most popular of the Armstrong family, Alex being the second.
 * Major General Armstrong was the only female member of Central's High Command, as well as the highest-ranked woman depicted in the FMA series.