For the superweapon from Ace Combat Infinity, see Stonehenge (Infinity). For other uses, see Stonehenge.

"Is the distance to the target correct? Holy... that thing is huge!"
ISAF pilot upon seeing Stonehenge[3]

Stonehenge,[a] also known as the Spaceguard Turret Network (STN),[4] is a railgun complex constructed in western Usea. It is located in the Hatties Desert[5] and in close proximity to San Salvacion.[6] It is the primary weapon developed at the end of the 20th century to address the threat of the Ulysses 1994XF04 asteroid. Its eight railguns succeeded in destroying some Ulysses fragments but could not protect Usea completely, and one of its railguns was disabled by one such fragment.[7]

The former Federal Republic of Erusea captured Stonehenge in 2003, compelling other Usean countries to form the Independent State Allied Forces (ISAF). Erusea used Stonehenge as an anti-aircraft weapon against ISAF throughout the ensuing Continental War. Mobius 1 eventually destroyed the seven operational railguns in April 2005.

In 2019, the Osean Ground Defense Force modified and reactivated the disabled railgun during the Lighthouse War. Osea used it to destroy one of the Erusean-controlled Arsenal Birds. Without proper cooling, the railgun could only fire once, preventing it from being used again in the future.[2]


During Ace Combat 04: Shattered Skies development, the world of Strangereal bore many similarities to our real world.[8] In-univese material written prior to the game's launch stated that the design of the railgun complex "[evokes] images of ancient times—of Stonehenge",[6] referring to the Stonehenge monument in England and leading to the weapon's nickname. As of Ace Combat 7: Skies Unknown, there remains no evidence of a similar monument on Strangereal's version of Earth.



STN Overhead

A bird's-eye view of Stonehenge, photographed on January 15, 1999[9]

"This battery of guns which stare down the heavens is the keystone of our salvation ... A space guard system like this had been advocated before, but there has never been a plan this concrete until now."
Titan Guns[6]

The Federation of Central Usea (FCU) kept the Ulysses impact a secret "due to political and cultural considerations" and convened an aerospace conference to discuss how to combat the asteroid. The conference ended in a clear consensus that the FCU would have to cooperate with its allies to develop a countermeasure. On April 20, 1996, FCU President Robert Sinclair disclosed the asteroid's existence to the world in a public news conference. That same day, the FCU Secretary of State attended an emergency assembly of the Central Usea Treaty Organization (UTO) where various defense proposals were made.[10] Later that spring, the FCU conceived a defense initiative of using a railgun network to protect the continent. This became the STN program, and Stonehenge thus began development.[6] Some believe that Stonehenge was already secretly in development prior to the April 20 Ulysses reveal.[9]

A Usean aerospace committee ultimately chose to construct Stonehenge in Area 26021-3,[11] a site in the Hatties Desert region[5] south of San Salvacion. As soon as the news broke, 15,000 civilians from San Salvacion formed a "human ring" in the area, protesting the construction due to the area's historical background and the fear of UTO military presence. Despite the protests, Stonehenge's construction proceeded.[6]

STN Construction

Construction crews assembling Stonehenge

The site's development was overseen by an executive committee and branched into at least 28 different design departments. Security was provided by a fighter squadron under command of the UTO; among the pilots was John Herbert, a veteran of the Usean coup d'état.[6] Many countries, private corporations, and scientists from around the world participated in the construction effort, led by the FCU and the UTO. Among the scientists were Dr. Jan Tomic[6] and David Hartmann, the latter hailing from Belka.[12] The Osean Federation and Union of Yuktobanian Republics considered joining the project, but declined on account of post-Belkan War reconstruction efforts.[1][13]

The main STN site was completed in June 1998,[1] though the railguns themselves remained under construction for several more months.[6] The International Astronomical Union also released an updated report on Ulysses in June 1998. The report expanded the projected impact area to the Anean continent. Stonehenge was too far in its development to extend its range and cover Anea, sparking protests in the continent against the FCU. Anean countries were left to develop their own means of defense.[14]

By September 1998, Stonehenge's engineers completed test firing of railgun one. Dr. Jan Tomic described the progress as "about 80% complete" to World News reporters who arrived at Stonehenge for a special issue, "Titan Guns".[6]

Ulysses Impact Event and takeover[]

Stonehenge Soldiers

Erusean soldiers occupying Stonehenge

"Erusea has secured not only the facility, but also the knowledge and manpower to operate it ... What should concern us most is what Erusea will do now that it has possession of Stonehenge ... were this facility to fire another round, we can be sure its target wouldn't be a meteorite."

On July 3, 1999, Stonehenge commenced operations against Ulysses, limiting damage across the Usean continent during the impact event.[7] Despite being the only weapon successfully operating during the impact, Stonehenge could not prevent all of the carnage; over 500,000 Usean civilians perished in the first two weeks of the planetfall.[15][16] In addition, railgun four was disabled by a nearby meteorite impact[7] and remained out of commission for 20 years.[3][5]

In the aftermath of the Ulysses Impact Event, the Federal Republic of Erusea was overwhelmed by an influx of refugees, compelling Erusean officials to restrict the issuing of visas to refugees.[7] As tensions escalated with the international community, the Erusean military—without warning—invaded San Salvacion in the summer of 2003. The Erusean Air Force performed aerial bombing runs, followed by a three-day ground offensive by the Erusean Army. During this time, the Erusean Air Force shot down the UTO aircraft assigned to protect Stonehenge, and Erusea captured the facility as well.[17] These events caused great worry within the international community. In an official statement, Erusea declared that Stonehenge's management staff was kept "under protection" and in good health by its troops, but this could not be confirmed.[7]

Yellow Squadron Vertical Over Stonehenge

Two Yellow Squadron aircraft flying vertical over Stonehenge

On August 22, 2003, FCU President Robert Sinclair sent Erusea an ultimatum threatening military action if they did not remove all occupying forces from San Salvacion and Stonehenge by September 14.[7][1][18] The FCU military began to amass around San Salvacion in advance. President Sinclair also announced the formation of the Independent State Allied Forces in preparation for all-out war.[7]

Erusea implemented a complicated chain of defense to maintain its hold on Stonehenge. It consisted of the Stonehenge railguns themselves, Erusea's Missile Air Defense Force for short-range defense, and the Erusean Air Force—including the elite Yellow Squadron—for long-range defense. Grudges between members of the Missile Air Defense Force and the Air Force limited their functionality, and their overlapping responsibilities led to Stonehenge accidentally shooting down an Air Force plane. Erusea cut back the Air Force presence to just Yellow Squadron and a handful of other pilots, but the facility's defensive capabilities were deemed less secure as a result.[19]

Continental War[]

Stonehenge Espionage Mission Intel

A reconnaissance photo of a Stonehenge railgun

"...the combat losses due to Stonehenge were higher than expected. Victory will elude us until it is eliminated."
― ISAF briefing officer following Operation Blackout[20]

On September 14, 2003, the ISAF dispatched an elite squadron to perform a surprise attack to destroy Stonehenge. The mission failed after Erusea's elite Yellow Squadron shot down all of ISAF's aircraft.[16] ISAF also sent special engineering forces to sabotage Stonehenge. The operatives captured an image of the railguns and transmitted it back to ISAF, but Erusean soldiers detected the side lobe radiation generated by the transmission. The operatives were discovered and the sabotage operation also ended in failure.[21][19]

After its retreat from the mainland and the relocation of its headquarters to North Point, the ISAF began making retaliatory strikes in preparation for a counterattack. Shortly after the capture of Stonehenge, the Erusean government announced its plan to produce X-02 Wyverns to serve as the superweapon's protectors, sparking debate within the Erusean Parliament over their cost and efficacy, which eventually halted the X-02's production.[22][23]

During the ISAF's counteroffensive operations within mainland Usea, Erusea used Stonehenge to attack the ISAF with limited success. In March 2005, several engineers and scientists responsible for designing the weapon, who had been detained by Erusea under the pretext of "security purposes", escaped with their families on-board Air Ixiom Flights 701 and 702. In exchange for protection and amnesty, the engineers offered to provide ISAF with crucial information regarding Stonehenge's defensive systems. ISAF ace Mobius 1 was dispatched to escort and defend the airliners from Erusean fighters until their safe arrival within ISAF territory.[24]

Stonehenge Cannons

The Stonehenge railgun turrets ready to fire

A month later, on April 2, the ISAF launched a second aerial attack on Stonehenge. The effort, Operation Stone Crusher, resulted in the complete destruction of the seven operational railguns due to Mobius 1's intervention. Yellow Squadron scrambled from nearby San Salvacion to intercept the ISAF squadrons, but was forced to retreat after Mobius 1 shot down Yellow 4.[3]

Lighthouse War[]

Stonehenge Power Trucks

Stonehenge being powered by Osean generator trucks

"Are we sure that thing's even going to fire? Seriously, I mean how old is it?"

During the Lighthouse War, the Cyclops and Strider Squadrons were tasked with reconnaissance on Stonehenge and its surroundings.[25]

Later in the war, forces from the Osean Ground Defense Force, led by Major Deanna McOnie and Warrant Officer Lehmann, secretly reactivated the fourth railgun that was previously disabled by a Ulysses meteorite impact. This operation was undertaken with the intention of eliminating at least one of the Arsenal Birds. Instead of using the facility's power circuit damaged by the meteorite impacts, multiple trucks carrying power banks were used to power the railgun.[5]

During the operation, multiple Osean Air Defense Force and OGDF units defended the railgun from invading Erusean forces. The Arsenal Bird Liberty later entered the airspace. As the battle progressed, the survey team was killed by an Erusean agent, forcing the team to visually aim the railgun. Trigger and Cyclops 1 were also tasked with destroying the main propellers in order for the Arsenal Bird to slow down, giving the railgun a clear shot. As the Arsenal Bird activated its shield, the railgun was fired, penetrating the shield and splitting Liberty in half, crashing in the vicinity of Stonehenge. Upon successfully firing, the railgun broke down, effectively rendering the entirety of Stonehenge inoperable.[5]


One of humanity's foremost projects built to combat the threat of Ulysses, Stonehenge was based on a circular design divided into eight sections, each of which housed a railgun turret.[6] The weapons, officially called the "120 cm anti-air-and-surface, gunpowder-and-electromagnetic hybrid acceleration-based semi-automatic fixed-gun system",[17] operated on a hybrid energy principle using gunpowder to initially propel projectile shells, and then accelerate them to maximum velocity with electromagnetic energy.[6]

The cannons were considered "electromagnetic launchers" by their creators instead of true railguns, due to the combination of propellants utilized. Capable of accelerating projectiles to a velocity of six kilometers per second (about 17-18 times the speed of sound), Stonehenge's hybrid propellant system was chosen to prevent excess heat from warping the barrels and lower the cost of its electricity consumption. The weapons were originally planned to be locomotive, but the idea was quickly abandoned because a capacitor suited for such operations was technologically unfeasible.[6]

Stonehenge (Complex Illustration)

Concept art of the STN facility

Stonehenge's turrets were directed by a synthesized control network beneath the facility formed by a complex of 8,192 supercomputers split into 1,024 sets of eight; each was capable of performing nine billion floating point arithmetic operations per second. Stonehenge was capable of performing a total of 100 trillion operations per second using all of its computational power. The system also employed data gathered from orbiting satellites, observatories around the globe, and weather models of Usea's atmospheric conditions to calculate an asteroid's destined point of impact. The computers aiming the cannon(s) would then plot the asteroid's trajectory, track the target, and fire.[6] The cannons were also provided with range tables to allow analogue targeting in the event that the control network failed.[5]

As a whole, Stonehenge's firing range encompassed a radius of 1,200 kilometers,[6] spanning from Erusea's capital of Farbanti on the western tip of Usea to the Faith Park region. The cannons could launch a variety of ammunition, including armor-piercing explosive rounds and a special type of shell suited for large fragments, whose use was limited under a special measures act.[6] The projectiles were strong enough to destroy a moderately damaged Arsenal Bird in a single hit through its shield.[5]




  1. Stonehenge (ストーンヘンジ)[4]