Senjutsuki (戦術機, "tactical fighter"), or senjutsuhokousentouki (戦術歩行戦闘機, "tactical walking fighter aircraft"), are large bipedal machines, and are a primary weapon system used to combat the aliens known as the BETA in the BETA War World. The Beings of Extra Terrestrial origin which is Adversary to the human race, more commonly known by the acronym BETA, are extraterrestrial lifeforms.

Tactical Surface Fighters

In the alternate timelines of Unlimited and Alternative, the invasion of Earth by the BETA began in 1974. To circumvent the overwhelming anti-air superiority of the Laser-class BETA, TSFs were thus developed as all-purpose assault units, able to fight in urban areas, on uneven terrain, and 3-dimensional combat within the interior of BETA Hives without their maneuverability being constrained in the heat of battle, following the successful deployment of bipedal mechanized units such as the Feedback Protector and NCAF-X1 used in the preceding First Lunar War. Since their first deployment in 1974, TSFs have become essential to humanity's survival over the 30-year war.
TSF movement is a combination of bipedal locomotion and thrust from their Jump Units. Their legs and arms are moved with carbon actuators, superconducting bands of carbon-based material that expand and contract based on the electrical current passed though them; the electricity to power the carbon actuators come from a combination of batteries and magnesium fuel cells. Jump Units produce thrust by processing specialized jet fuel, usually stored in the Jump Units themselves or in storage tanks in a TSF's legs. External tanks can be attached to a TSF for increased operational time and distance.
TSF mobility is further enhanced by their joint construction; the combined usage of carbon actuators and multiple joints structures in a single joint segment impart TSFs with high operating limits and shock-absorbing capabilities during battle.[3] One example is the wide-ranged rotational capability of a TSF's shoulders and elbows, allowing them to engage targets directly behind them even without gun-equipped Mount Pylons.[3] Sub-arms positioned underneath the shoulder-block armor allow TSFs a wide range of arm movement without interference.
Mobility is not just all that TSFs have, however; they are also armored in an anti-projectile and heat-resistant composite that has been further treated with anti-laser coating. Armor on the upper body segment also aids in maneuverability by improving the active instability aspect of a TSF; a higher center of gravity improves the execution time of maneuvers during combat. However, with the immense power wielded by the Laser-class BETA, armor protection for TSFs remains a low-return concept compared to attack avoidance.
TSF development can be split into three distinct generations, with each generation an indicator of their technology level and advancement. However, the generation standing is not a direct indication of combat strength in any capacity.

BETA Life Forms

As an alien force created for mining, the BETA center their strategies around total dominance with overwhelming numbers; the areas that they take are eventually mined of all possible resources, leaving a barren wasteland behind that is unfit for supporting human life for decades to come. What allows them to not just stand toe-to-toe with humanity's forces, but to actually dominate them, however, are the Laser-class and Heavy Laser-class BETA. Their lasers can instantly destroy both air and ground enemy units from beyond visual ranges, and due to the fact that a typical low-threat BETA encounter would usually number several dozen Grappler-, Tank-, and Destroyer-class means that without air support, human armies would typically find themselves outmatched and outnumbered in a ground war. The laser classes also prioritize targets based on the computer systems they have, thus making missiles and drones higher priority targets than artillery shells. The more advanced the higher the priority. However, this later changed to give higher priority to manned systems, thus making TSFs which have powerful computers as well as having a human pilot a higher priority for the Laser class BETA.
In addition, there is no real way to detect a BETA offensive from far off; ground-based sonic sensors and recon satellites are at the mercy of the weather and mechanical failure. The best defence is to have pilots being able to respond quickly and efficiently to a sudden incursion, and to quickly deal with an incoming force if it is detected early enough. During an offensive push by the BETA, expect to see several hundred to tens of thousands of Tank-, Grappler- and Destroyer-class, as well several Fort-class and dozens if not hundreds of Laser/Heavy-Laser-class BETA in the mix as well.
The BETA are usually commanded by the Superior, a BETA strain best described as a "biological quantum computer". This is the one true threat to victory in any engagement; the BETA in general can be lured into traps or defeated with clever use of tactics, but when led by a Superior, the BETA become noticeably smarter, to the extent where it understands the concepts of human tactics and will create ways to counter them. Some basic tactics used by the BETA include tunneling from underground, often surprising defending forces from the rear, or from another front, creating opportunities for overconfident pilots to get trapped in a pincer maneuver. Often the main issue with combating BETA in any prolonged engagement is the threat of running out of ammunition, and the massive numerical odds; close-quarters combat is viable, but that would be playing into the area of strength for the BETA, and is not encouraged unless as a last-ditch measure.
BETA force size organization, as is expected of their force composition, is several times higher than their human counterparts. To add to that, most major engagements take place with multiple corps-sized formations deployed by the BETA, as is their nature to rely on overwhelming numbers.