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Sikowsky on Requiem in February 2558, in the location known as "Two Giants".

Sikowsky on New Zaječar in November 2558.

Sikowsky Unarmored.png

Leon Sikowsky
Biographical information

Sikowsky, Leon K.


Reach (New Alexandria, Eposz)

Date of birth

May 14, 2532




6 feet, 4 inches

Hair color


Eye color


Affiliation and military information

Spartan Team Leader (SR-106)


Fireteam leader


Active as of May 2560


Class II


Spartan Leon Sikowsky (callsign Valiant One) was a UNSC Army trooper who fought in the final days of the Human-Covenant War. After the war's conclusion, Sikowsky was selected to become a SPARTAN-IV supersoldier, and was transferred to a new branch of the UNSC military known as Spartan Operations. Sikowsky was placed in command of Fireteam Valiant shortly after.


Early Life

Leon was born to Kaitlyn Sikowsky, a well-to-do delinquent teenage youth from New Alexandria, Reach who became pregnant at the age of fifteen after an alcohol-fueled one-night-stand with a young man (whom she would later be unable to remember due to how drunk she was) at a house party in 2531. Becoming pregnant however motivated Kaitlyn to get her life together for the sake of her unborn child. Supported financially by her parents, Kaitlyn put renewed effort into her schoolwork, enough to enable her to make up for her earlier poor grades and get accepted to a local university there in the city several years later.

From his birth, Leon was strange. He sometimes disliked being held as an infant. As a toddler, he would not play with his toys when others were around, and he preferred to organize his toys rather than to truly play with them as well. In school, he associated little with other children, and performed badly in his academics despite showing exceptional intelligence for his age.

Concerned, Leon's school had him tested for Asperger Syndrome, a form of high-functioning autism, and the results were positive.

After his diagnosis, Leon was placed in a special education program, which gave him access to adaptions in his academics, and also taught him how to better socialize with children his age. Thanks to the help of this program, Leon was able to do well in school and make plenty of friends. However, Leon never managed to have much luck in dating during his adolescence, despite plenty of interest.

After graduating from high school, Leon decided to join the UNSC Army with his good friend Jacob Steinworth, who was determined to help keep the looming Covenant threat from reaching Earth.

Military Service

Human-Covenant War

Fall of Reach
Battle at Szurdok Ridge

Sikowsky fighting in the Szurdok Ridge.

After about one uneventful year following the completion of Leon's training, the Covenant finally arrived on Reach. A small special operations team discovered an enormous Covenant invasion force secretly massing in Ütközet, and Leon and Jacob found themselves being deployed as part of a massive offensive aimed at dismantling the Covenant invasion before it even began.

Early in the battle, Leon's Falcon broke off from the main assault force to aid in the destruction of several Covenant anti-aircraft guns that were preventing the Navy from providing vital air support. Leon's platoon was deployed at a Covenant-occupied BXR mining facility between the AA guns, and attempted to clear the building to allow ground forces to pass through it. However, the platoon quickly sustained heavy casualties, and were forced to evacuate the premises of the facility via Pelican. After dropping off their wounded at base camp, the remainder of Leon's platoon was redeployed to secure the ruins of one of the anti-aircraft guns, which had been destroyed by a lone specialist operator.

However, after the UNSC Grafton destroyed a Covenant teleportation spire and revealed a Covenant supercarrier in geosynchronous orbit above Ütközet, the UNSC began to hastily withdraw their forces from the region. Leon and Jacob were sent to their hometown of New Alexandria, which, being a major population center, would be a prime target for the Covenant invaders.

Siege of New Alexandria

Sure enough, New Alexandria fell under attack by four SDV-class heavy corvettes soon after the supercarrier over Ütközet was destroyed and Covenant reinforcements arrived in orbit. The Corvettes began to deploy Brute shock troops throughout the city, who quickly took control of key locations and making civilian evacuation difficult.

Battle for Earth

Post-Covenant War

Becoming a SPARTAN
Battle of Requiem
New Phoenix Incident
Requiem Campaign
Attack on the UNSC Orphellion
Joining Operational Detachment-Sigma
Raid on New Zaječar
Steinhold Rescue Operation
Mission to New Babylonia
Theras Outbreak

Career Service Vitae

Leon in his MJOLNIR armor.
Sikowsky, Leon
Spartan Team Leader (SR-106)

FULL NAME: Leon Kurtis Sikowsky
SERVICE #: 75526-26721-LS

    Unit: Fireteam Valiant
    Enlistment Date: 11/06/2550
    Location: UNSC Vegas

    Gender: M
    Birthplace: New Alexandria, Eposz, Reach
    Birth Date: 05/14/2532
    Blood Type: O+
    Height: 193.04 cm
    Weight: 89.3577 kg

General Notes

Sikowsky has Asperger Syndrome, a high-functioning Autism Spectrum Disorder. While this impacts some of his skills regarding organization and social interaction, it does not affect him much at all as a soldier. Sikowsky is a perfectly if not exceptionally capable fighter. Sikowsky's IQ and understanding of technical subjects are also well above average.

Sikowsky has been grafted into the SPARTAN-IV program [REDACTED] He has been placed in command of Fireteam Valiant, despite being one of the youngest and least experienced members of the team. However, Sikowsky is the most natural leader in the group, and the other members of Fireteam Valiant (with the possible exception of Spartan Corin Davis, though it should be noted that Davis has on multiple occasions been stated as being somewhat insubordinate) seem to trust his judgement. This trust is impressive, considering the reputations of some of his teammates (Spartan Davis is a decorated soldier whom has spent most of his career as an ODST, and Spartan Dorton is a former member of the highly exclusive 21st Fallschirmjäger Regiment of Germany's UNSCDF 6th Army). His place as Valiant's leader [REDACTED]

Performance & Equipment

Sikowsky and his team are all consistently ranked within the top 20% of Spartans aboard the Infinity, and he is proficient in all simulation modes featured on the Infinty's holographic training deck. He prefers the standard deathmatch-style modes known colloquially by Spartans as "Slayer", but performs well in all scenario types.

Based on data gathered through the simulations, Sikowsky favors the MA5D ICWS and the M6H PDWS heavily. He also appears to prefer to engage foes at a shorter than average range.

Sikowsky uses the Warrior variant of the MJOLNIR [GEN2] PAA, which affords him the ability to operate relatively effectively in a wide range of combat scenarios. He also utilizes an upgraded VISR 4.05, which prevents moisture from adhering to the visor, so that it does not freeze and limit visibility in subzero conditions. [REDACTED]

Service History


Special Notice[s]

Spartan Leon Sikowsky filed a Personal Relationship Form on October 30, 2556, and is thus officially recognized by the United Nations Space Command Defense Forces as being involved in a romantic relationship with UNSC Navy civilian attaché Dr. Annette Darvinshire. As such, Spartan Sikowsky and his partner are obligated to conform to all official UNSC codes and regulations relating to personal relationships of this nature. As of this date (October 3, 2558) no violations have been made by Spartan Sikowsky and/or his partner, nor have any request[s] for a termination of this contract been made to date.

Personality & Traits

"I met some real Spartans back during the war, you know. Man, when I think about them, sometimes I wonder if us IVs are just Spartans in name only."
―Sikowsky, on the differences between the SPARTAN-IIs and the SPARTAN-IVs.

Unlike many SPARTAN-IVs, Sikowsky did not let becoming a Spartan go to his head, and he remained humble and down to earth, and looked down upon those Spartans whose egos swelled from their newfound abilities. Sikowsky tried to model himself after the Spartans of Sapphire Team whom he'd fought alongside during the war, and he encouraged his comrades to behave similarly.

Due to his Aspergers, Sikowsky often struggled with being patient and maintaining his focus. Though this would improve over time, it would remain an area of weakness for him throughout his military career. However, when he did allow himself to stop, think, and analyze a situation, Sikowsky was an excellent tactician. Unlike many autistics, Sikowsky was very skilled at reading both people and situations, something which helped him greatly as a soldier and a leader.

Socially, Sikowsky fared well, appearing mostly normal. However, he did exhibit a few quirks, such as a tendency towards overenthusiasm, and some minor obsessive-compulsive habits. While his friends and teammates became accustomed to these things, and a few, such as Annette Darvinshire, even found these traits endearing, others like Sarah Palmer found these habits annoying and would lose patience with Sikowsky very quickly.



Leon Sikowsky's MJOLNIR suits
Suit Name
Time Worn
Sikowsky Equip Recruit.png
December 9, 2554—April 21, 2555
Issued to all newly-augmented SPARTAN-IVs, RECRUIT-class MJOLNIR is designed to allow one's body to adjust to the stresses of wearing the MJOLNIR PAA. Rather than use the standard steel and gold scheme of the rest of Infinity's Spartan contingent, Sikowsky customized his suit with a steel and dark green color scheme in a unique pattern, although this customization remained compliant with UNSC Equipment Code 20.00.62.
Sikowsky Equip Warrior.png
April 21, 2555—
After graduating from the Recruit armor, Sikowsky was presented with the option to either keep fielding the Recruit armor, or transition to one out of a small list of MJOLNIR variants selected specifically for him. Sikowsky ultimately chose to transition to WARRIOR-class MJOLNIR, commonly considered by many to be the [GEN2] platform's baseline variant, and easily its most popular. This armor variant allowed for exceptional speed and mobility, while at the same time allowing for minimal compromise in regards to protection. Sikowsky retained the steel and dark green scheme from his previous Recruit armor, and also added the VISR 4.05, or the "Frost" visor. In May 2558, this armor was upgraded with an integrated thruster pack as part of a system-wide update. Additionally, after transferring to the UNSC Orphellion in July 2558, Sikowsky would repaint his armor, using a new pattern and two different shades of green instead of just one.


Leon Sikowsky's Weapons
Weapon Name
Date Issued
MA37 Individual Combat Weapon System
February 22, 2551
MA5D Individual Combat Weapon System (2554 model)
July 17, 2554
MA5D Individual Combat Weapon System (2558 model)
June 8, 2558
M6H Personal Defense Weapon System
July 17, 2554
M6H2 Personal Defense Weapon System
June 8, 2558
M11 Combat Knife
M11 CK.png
July 17, 2554
Any and all weapons and equipment required based on mission parameters and/or objectives



  • After transferring to the UNSC Orphellion, Sikowsky repainted his MJOLNIR armor. This explains the difference between his armor's paint scheme in Halo 4 and Halo 5: Guardians.

List of Appearances

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