Battle of Earth
In the alternate reality, the Battle of Earth was a conflict fought on stardate 2258.42 between the Romulan starship Narada and the  of the United Federation of Planets.

Prelude
Following the destruction of Vulcan, the Narada plotted a course for Earth. The Naradas captain, Nero, tortured Captain , who was captive on board the Romulan mining vessel, using a Centaurian slug to coerce Pike to reveal the security codes to Earth's planetary defense system. He revealed his intention to Pike to destroy the homeworlds of the Federation one at a time.

, who was now in command of the , planned to fall back with the primary fleet in the Laurentian system. However, his first officer, , felt that they needed to find a way to engage the Narada immediately and rescue the captured Pike. After a brief brawl, Spock ordered Kirk marooned on , an ice-bound Class M planet in the Vulcan system with a Federation outpost. It was there that Kirk met a much older Spock, from the future, who explained to him what was really going on. Realizing that the timeline had changed because of his and Naradas presence, and knowing that his younger self would never make the decisions needed to save Earth and the Federation, Spock decided to help Kirk get command of the Enterprise.

Kirk and this Spock made their way to Delta Vega's Federation outpost, whose only occupants were  and Keenser. Scott had been stationed on Delta Vega six months previous after a transporter experiment went awry and resulted in the loss of Admiral 's prized pet beagle. He was trying to prove a theorem in transwarp beaming. Spock took the opportunity to give Scott the completed calculations for transwarp beaming: the only thing Scott had forgotten was to take into account that space itself was moving.

Spock planned to beam Kirk and Scott aboard the Enterprise while he and Keenser stayed behind on Delta Vega. He told Kirk that the only chance to stop Nero was for Kirk himself to take command and he could do so through Starfleet Regulation 619, which dictates that a commanding officer must relinquish their command if the mission at hand leaves them "emotionally compromised". He refused to come with them stating that it was not his destiny and that his self of that timeline must never know of his presence due to dangerous consequences.

Kirk and Scott were successfully beamed into Engineering on board the Enterprise, but Scott ended up beamed into a holding tank in the ship's water treatment system. Soon after Scott was freed from his predicament, he and Kirk were captured and brought to the Bridge. There, Kirk challenged how calm Spock was after the destruction and the death of his mother, , provoking Spock to attack him. Kirk found himself being strangled against the helm console before Spock was stopped on command from his father, , who was on the bridge at that time. Realizing what he had done, Spock relinquished command under Regulation 619, and left the Bridge. Kirk then took command, and began working on finding a way to overpower the Narada with the crew.

The navigator of the Enterprise, , came up with an idea. He calculated that the Narada would pass by Saturn on its way to Earth. He reasoned that if they warped into Saturn's system and remained behind Titan, they could use magnetic interference from Saturn's rings to remain undetected. Assuming it hadn't already fired its drilling beam, they could use Scott's transwarp beaming calculations to beam someone on board the Narada. 

At this time, Spock, after a talk with Sarek about the loss of his mother, returned to the Bridge and confirmed Chekov's calculations. Spock volunteered to beam aboard the Narada; since Romulans and Vulcans share similar cultural traits, it would be easier for him to figure out where the Naradas black hole device was. Kirk decided to go with him, ignoring Starfleet regulations about commanding officers beaming into dangerous situations. They also hoped to rescue Captain Pike while aboard the ship.

The battle
By the time Enterprise has arrived, the Narada was already at Earth. It was lowering its drilling beam over San Francisco, home of Starfleet Command. The Enterprise emerged from warp in Titan's upper atmosphere, and helmsman Hikaru Sulu used impulse engines and thrusters to lift out of Titan's atmosphere and enter orbit.

Scott tried to beam Kirk and Spock into the Naradas cargo bay, but ended up beaming them into another part of the ship that was heavily trafficked by its crew. This resulted in an intense phaser firefight. Kirk and Spock eventually reached a defensible position, avoiding their disruptor fire and killing most of the Romulans in the vicinity. One was left alive, stunned by Kirk's phaser. Kirk covered Spock while the latter used a mind meld on the stunned Romulan. He succeeded in determining the location of the "black hole device" and Captain Pike. Shortly after Kirk and Spock were beamed aboard, the Narada fired its drilling beam, cutting it off from the Enterprise. Kirk and Spock were on their own.

The "black hole device" turned out to be a ship, the . When Kirk and Spock boarded the ship, it immediately recognized Spock as its owner, and gave its registry date as 2387. It was here that Spock realized what was going on. When Kirk asked Spock if he could pilot the ship, Spock reasoned that he probably already had.

While Spock took off in the Jellyfish, using its weapons to blast its way out of the Narada, Kirk found his way to the ship's bridge. He grappled briefly with Nero until Spock used the Jellyfishs weapons to shoot down the Naradas drilling platform, ending its drilling on Earth well before it could reach the planet's core. The platform fell harmlessly into San Francisco Bay, barely missing the Golden Gate Bridge. 

Nero left in a rage to go after the Jellyfish, leaving his first officer, Ayel, to deal with Kirk. While Ayel was able to overpower Kirk with relative ease, this made him overconfident, and he failed to realize that Kirk had stolen his disruptor until the Human, offered last words, let him know it just before shooting and killing him. Kirk then located and freed Captain Pike, who was left injured as a result of his earlier torture - during this time two Romulan guards had entered the chamber and discovered what was going on, but upon seeing them Pike grabbed Kirk's sidearm and shot both intruders before his savior even knew of their presence.

The Jellyfish was able to warp away before a volley of torpedoes from the Narada could hit it. The Narada pursued the Jellyfish to a remote part of the Sol system. Spock laid in a collision course with Narada, which would ignite its remaining stockpile of red matter. Nero attempted to shoot the Jellyfish down with every remaining missile he had. At that point, the Enterprise appeared out of warp right behind the Jellyfish and destroyed all of the missiles aimed at it. The Enterprise was able to beam Spock, Kirk and Pike on-board before the Jellyfish collided with the Narada, igniting the red matter on board the Jellyfish and creating a black hole in the Narada.

Kirk offered assistance to the Narada, but Nero defiantly refused. The Enterprise turned its weapons on the Narada, breaking the ship up and hastening its consumption by the black hole. Once the Narada was completely destroyed, however, the Enterprise found itself trapped in the black hole's gravity well, unable to move away even at maximum warp. Scott ejected several of the ship's warp core segments and detonated them near the black hole, helping push the Enterprise to safety.

Aftermath
On Earth, Spock finally met the other Spock from the future of the prime reality. Spock was considering resigning his commission to assist with the rebuilding of Vulcan civilization, but his prime universe counterpart insisted that Spock "for once, put logic aside and do what feels right" and remain in Starfleet. Spock Prime had already found a suitable planet where the survivors of planet 's destruction could begin the work of rebuilding their race. Following the incident, Christopher Pike required the use of a wheelchair as a result of his ordeal on the Narada. In light of his role during the battle, Pike was promoted to the rank of Admiral.

For his heroism and quick thinking, James T. Kirk was promoted directly to Captain, and was assigned permanently to command the USS Enterprise in relief of Admiral Pike. A previous inquiry at  concerning Kirk's actions in his third taking of the Kobayashi Maru test was dismissed. Kirk chose many of the cadets who were assigned to the Enterprise during the Narada crisis as his senior officers, including helmsman , navigation officer , communications officer , chief medical officer Dr. , and chief engineer  (who also brought Keenser along as part of his engineering staff). He would also choose  as his first officer when the latter offered his candidacy for the position. ()

External link 

Conflicts (alternate reality)
Earth conflicts