Admiral Marcus's History
Fleet Admiral Alexander Marcus was the head of Starfleet in the mid-23rd century, and a member of Section 31. He began a conspiracy to start a war with the Klingons using the 20th century genetically-enhanced Human criminal Khan. He was the father of Carol Marcus.
Alexander Marcus was the head of Starfleet. At some point, Marcus had a daughter named Carol with a woman who had the maiden name Wallace. He was also the mentor of Christopher Pike and inspired him to join Starfleet. Having been raised by him, Carol believed (ultimately incorrectly) that her father was incapable of killing innocents.
Following the destruction of Vulcan in 2258, Marcus began seeking ways to militarize and better defend the Federation. In particular, he considered war with the Klingon Empire as inevitable. Section 31 discovered the SS Botany Bay, which led to Marcus reviving Khan Noonien Singh and recruiting him under the name "John Harrison" to design weapons and ships.
However, Khan resented Marcus' control over him and the use of his fellow surviving Augments as hostages, and attempted to smuggle them out in the experimental photon torpedoes he created. Unfortunately for him, Khan was discovered, forcing him to flee alone, and he began a one-man war on the Federation as he presumed that Marcus had killed his crew.
In 2259, when Captain James T. Kirk violated the Prime Directive while on Nibiru, the matter was brought to Marcus' attention who, as punishment, confiscated the USS Enterprise from him and sent him back to Starfleet Academy. However, Pike convinced Marcus to alter the punishment for his protégé. As such, Kirk was instead demoted to Pike's first officer.
On stardate 2259.55, Khan coerced Section 31 agent Thomas Harewood into bombing the Kelvin Memorial Archive in London. Marcus received a transmission from Harewood before he died explaining Harrison had threatened him, and the admiral declared a manhunt at a summit in Starfleet Headquarters. Aware that protocol dictated a summit like this one, Khan appeared in an attack vehicle and opened fire. However, Khan was forced to flee and Marcus survived, though Pike was killed.
The following morning, Kirk reported that Harrison had used the confiscated transwarp beaming formula to escape to Qo'noS. Marcus ordered Kirk to pinpoint and execute Khan with the seventy-two experimental photon torpedoes he had designed.
Once Kirk discovered the truth from Khan, Marcus showed up in the USS Vengeance (a warship designed by Khan) with the intent to retrieve Khan and destroy the Enterprise and its crew to cover up his crimes. Refusing Marcus’s orders to hand Khan over, Kirk attempted to flee to Earth in the hopes of putting Khan on trial and exposing Marcus's treachery. However, the Vengeance caught up and crippled the Enterprise in warp space. Marcus's daughter Carol revealed herself to him on the Enterprise in a bid to get him to spare the ship and her crew, but the admiral simply had her beamed aboard the Vengeance and proceeded to order his crew to destroy the Enterprise. Fortunately, Montgomery Scott had smuggled himself aboard the Vengeance at coordinates given by Khan and deactivated its weaponry. Khan and Kirk donned thruster suits and flew over to the ship to commandeer the bridge, during which Khan saved Kirk's life when the display compass in Kirk's helmet went dead, leaving Kirk flying blind. Khan found Kirk amid the debris and guided him in.
After taking over the bridge, and believing that Khan intended to betray them, Kirk ordered Scott to stun Khan. Kirk then confronted Marcus over his betrayal of everything the Federation stood for, but Marcus furiously insisted that his actions were justified, and that without him, the Federation would be destroyed in what he considered to be an inevitable war with the Klingons, a war that he, ironically, was trying to start in the first place. Suddenly, having only pretended to have been stunned, Khan assaulted Scott, Kirk, and Carol. Marcus briefly escaped to a console near the back of the bridge, but before he could achieve anything, Khan caught up with the admiral and began crushing his skull with his bare hands, furiously telling Marcus that he should have let him sleep before killing him, prompting Carol to scream in horror.
Immediately after killing him, Khan took control of Marcus's ship and held Kirk, Scott, and Carol hostage, demanding that Spock surrender his crew or face destruction. Spock complied, allowing Khan to transport the seventy-two torpedoes to the Vengeance and transport Kirk, Scott, and Carol back onto the Enterprise. Having anticipated Khan's betrayal, Spock had ordered Doctor Leonard McCoy to remove the cryo tubes from the torpedoes and had them armed within the cargo bay of the Vengeance. The detonation crippled the ship and led Khan to believe that his crew were killed.
The battle caused both starships to fall down towards Earth. The Enterprise avoided crashing, but Khan directed the Vengeance into downtown San Francisco in an attempt to destroy Starfleet Headquarters in a final act of spite. He attempted to escape, but was apprehended by Spock and Nyota Uhura. Khan's blood was used to revive Kirk, who had suffered fatal radiation poisoning from saving the Enterprise, and he was placed back in stasis with the rest of his crew.
Nearly a year later, Kirk spoke at a memorial for the lives lost as a result of Admiral Marcus and Khan's actions. In his speech, Kirk reminded the attendees that Starfleet's true mission was not to militarize the Federation, but to explore the galaxy. As the rechristened Enterprise began to embark on the first five-year mission, Kirk expressed gratitude of Carol being part of the "family", to which she stated that it was nice to have a family.
