Allied assist

Yokohama Base Incident
Timeframe December 10, 2001
Location(s) involved Yokohama Base, Japan
Outcome United Nations victory
Known Belligerents
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United Nations

UN 11th Force

A207 Flight
A207 Squad A
A207 Squad B
Special Task Force A-01
3rd Tactical Armored Battalion
Sword Flight
Cracker Flight
Storm Flight
Axe Flight
Lancer Flight
Sobat Flight
Shark Flight
Falcon Flight
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Brigadier-General Paul Radhabinod (UN)
Captain Isumi Michiru (UN)

Professor Kouzuki Yuuko (UN)
- - -
Moderate loss of life compared to the scale of the attack. Total loss of attacking force.

The Yokohama Base Incident was a BETA attack on the United Nations 11th Forces' Yokohama Base on December 10, 2001. The attack on the base was a surprise assault on the UN forces, as they were in the midst of combat trials to evaluate the XM3 operating system for use in production units on the front-lines of battle.

Several flights of TSFs, in addition to newly-commissioned 2nd Lieutenants Shirogane Takeru, Mitsurugi Meiya, Ayamine Kei, Tamase Miki, Yoroi Mikoto, and Sakaki Chizuru of the A207 Flight participated in the XM3 Trials, and the subsequent combat that would later be identified as the Yokohama Base Incident.


XM3 TrialsEdit

The XM3 Trials, which aimed to evaluate the combat performance of XM3-equipped TSFs, consisted of several phases, with the full sequence of events conducted twice; once in the morning, once in the afternoon. The first was to test reaction speed by measuring the accuracy of any pilot against stationary targets in the training area while traveling at full speed. The targets' positions switched from time to time in order to randomize the test.

The next evaluation was done on the strain that XM3-equipped TSFs suffered to their movement control systems. Using a simple movement course, TSFs were required to move through the area towards the next point within a time limited taken from the average of twenty pilots of the 3rd Tactical Armored Battalion piloting a variety of TSFs. TSFs could either choose to move around or even over obstacles using boosted jumps, but were limited by how long they could stay in the air by the simulated presence of Laser-class BETA targeting aerial objects.

The final evaluation was to have the participating units fight against a simulated enemy, using TSF aggressor flights formed by veteran pilots in F-4Js using the old OS. The participating units were further reduced to three TSFs per flight to increase the difficulty level, with A207 split into two squads.

Nerf guns

F-4J engaging a practice target.

While most of the flights got through the first two phases without incident, the mock combat phase proved to be the most challenging. A207 Squad B, comprised of 2nd Lieutenants Shirogane Takeru, Ayamine Kei, and Yoroi Mikoto managed to successfully defeat their adversaries.

First evening out the numerical advantage by taking out one of the aggressors, A207-B and their opponents later entered a brief stalemate. 2nd Lieutenant Ayamine Kei's attempt at using her TSF as bait to break the deadlock proved unsuccessful, although the aggressors then took the initiative to engage A207-B in combat. Taking out his opponent after a prolonged gunfight, 2nd Lieutenant Shirogane Takeru then helped 2nd Lieutenant Yoroi Mikoto to chase his target into a pre-determined ambush zone to meet up with 2nd Lieutenant Ayamine Kei, who was also chasing her target into the same area. 2nd Lieutenant Shirogane Takeru eventually took out one more target using his Type-97's PB Knife but was shot down by friendly fire from 2nd Lieutenant Yoroi Mikoto, while 2nd Lieutenant Ayamine Kei shot down her own target.

Yokohama Base IncidentEdit

Ruitares have right of way

F-4Js facing a wave of Destroyer-class BETA.

Returning to the training grounds after the lunch period, A207 Flight continued to participate in the evaluation trials until unexpected disturbances began to occur in Area 2 of the training grounds. A Code 991 was soon announced, and BETA presence in the area was confirmed; Hornet Flight was the first to encounter the wave of Destroyer-class charging out of the building rubble that littered the training grounds, and were quickly reinforced by Sword, Cracker, and Storm Flights to block the BETA from advancing further. Axe, Lancer, and Sobat Flights were ordered to switch to combat gear at Hangar 27; standby units at Hangar 23 were ordered to change their weaponry and deploy. A207 Flight was grouped with Shark and Falcon Flights to delay the enemy advance. The process proved difficult due to the lack of artillery support, and the fact that none of the units on the field were outfitted for combat; the BETA continued their relentless advance before the helpless UN troops, while other units in reserve, including Special Task Force A-01, were being scrambled to meet this new threat.

The situation turned for the worse when artillery fire revealed the existence of Laser-class on the field of combat, severely restricting the available airspace in which units could maneuver. After seeing Flight A207 paralyzed with fear, Shark-1 requested permission to give them a Level-6 Combat Hypnosis program in conjunction with injected stimulants and then ordered the inexperienced soldiers to retrieve weapons from the Hangers. This calmed down A207 Flight with the exception of 2nd Lt. Shirogane Takeru who became extremely aggressive.

As A207 returned to the hangers, they were ambushed by a large number of Grapplers from the ground. The Squad Leader issued a scramble order and everyone obeyed except 2nd Lieutenant Shirogane Takeru who started screaming nonsensically and engaged the BETA, completely oblivious to all calls from his Flight to retreat and to the fact he was shooting at the BETA with paint balls. Despite charging madly at the enemy, and being massively outnumbered, 2nd Lieutenant Shirogane Takeru managed to unintentionally act as bait, drawing the attention of all the enemies (25 Grapplers according to the manga) in the area, and giving his squad a clear path to retreat. Furthermore, Shirogane's spraying of sticky paint on the ground managed to slow the nimble Grapplers.

Second Lieutenant Mitsurugi Meiya feared for 2nd Lt. Shirogane's safety and went to assist him with permission from her squad leader. She injected him with sedatives in an attempt to calm him down (Meiya injecting him with sedatives was retconned in the Muv Luv Alternative manga), but this backfired when 2nd Lieutenant Shirogane Takeru was left paralyzed long enough to be struck down by Grapplers. Captain Isumi Michiru of Special Task Force A-01 arrived at the same time, sent Squad 207 to the hangers, and quickly dispatched the BETA in the area. Afterwards she opened 2nd Lt. Shirogane's cockpit and commanded him to retreat to a nearby shelter, but because of the Lt.'s still undiagnosed PTSD he remained where he was out of sheer terror, long after Capt. Isumi had left.

Meanwhile, both the F-4J veterans and the XM3 equipped soldiers were faring poorly against the BETA, the Special Task Force A-01 and other armed troops were rushing to assist everyone, Squad 207 was acting as a convoy: rushing between the front lines and the supply base to deliver weapons to everyone, and the UN command was still in chaos. The unarmed pilots, equipped with either OS, were both losing their lives due to being unable to effectively stop the BETA; all they could do to stall the BETA's advance was to engage in evasive action after attracting their attention, which was swiftly dealt with by the BETA's superior numbers (The exception to this was 2nd Lt. Shirogane Takeru). Even soldiers that had deployed fully-armed, with the XM3, and in much, much superior units (Type-94 Shiranui) such as 2nd Lieutenants Tsukiji Tae (KIA) and Asakura (WIA), were unable to overcome the element of surprise the BETA possessed in the ruins of the training grounds, with half-collapsed buildings working as cover for the BETA's charge towards Yokohama Base.

It is unclear when the battle ended since the game skipped time, but since the BETA numbered in the hundreds instead of the usual tens, if not hundreds, of thousands it is very likely that they were swiftly dealt with because around late afternoon, before the sun had set, the training zone had already been declared free of all BETA. While damaged TSFs were in the process of being salvaged by non-combat personnel and survivors being searched for (e.g. medics in armored vehicles escorted by TSFs), a sudden code 991 was raised: a Soldier class BETA was seen eating an unidentified solider with another man. Captain Isumi opened fire with her 36mm gun, killing the BETA and destroying the UN soldier's body beyond recognition in the process, and then dispatched a medic to retrieve the 2nd Lt. who had relapsed into another PTSD episode and had lost consciousness from mental shock.

TSFs and support personnel were eventually sent out to hunt down the remaining BETA after the incident.


Using information obtained from 2nd Lt. Shirogane's interrogation, images captured from Captain Isumi's gun camera and from the DNA testing of the corpse, it was concluded that the solider that was killed was the Drill Sergeant Jinguuji Marimo. Her loss was a major setback due to her extensive abilities as a pilot, leader and her exceptional training capabilities as an Instructor. While her remains were sent to her parents, no one could offer an explanation why she failed to hear the half ton BETA walking behind her.

After reviewing 2nd Lt. Shirogane Takeru's exosuit data and comparing it with his data during the 12/5 Incident, Professor Kouzuki Yuuko diagnosed the soldier with Complex PTSD and officially sent him on a "high risk, cruel mission to the front lines", the nature of which remains classified.

The US government agreed to trade the XM3 for the XG-70 after witnessing the performance of the Special Task Force and an unarmed fresh graduate against the BETA.

The Japanese government finally decided to deploy the XM3, and it was given to them for free because of their support for Alternative IV. However, despite the government "dying to get their hands on the XM3" according to Yuuko, they publicly agreed to deploy it after trials by the 19th Independent Guard Flight in order to preserve the image of the IJA (i.e. not appear weak and as beggars in front of the UN and the world).

The results of the trials destroyed all skepticism towards the XM3 and both politicians and pilots who previously refused to adopt it were swayed.

Yokohoma's base overall attitude towards the war was changed. Prior to the trials, Professor Kouzuki Yuuko remarked that the soldiers were overall "lazy" because they believed the IJA stood between them and the BETA, and such slack in their duties and training. After the incident the entire base became more serious. For example, during a simple delivery of Type-94 Shiranui's, 2nd Lt. Shirogane noticed that the entire base was on edge and battle ready, wary of any possible problems. Furthermore, the old UN army generals were being replaced by war-hardened UN Army generals from every front.

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