This is my Metal Gear/ Shingeki No Kyojin crossover fanfic. I do not own Metal Gear, the Metal Gear series or any of its characters. I also do not own Shingeki No Kyojin, the series or any of its characters. This is a work of fanfiction.

…

The titans had found another way into the southern districts again, this time without the help of the Colossal titan, which was alarming, to say the least. Reports were flooding in from areas like Dauper village, which made certain members of the military worry more than others.

Armed with more efficient 3D gear, allowing them to stay airborne longer, as well as hardened blades and sharpshooter rifles loaded with armor piercing rounds, as well as the most cutting edge tank technology and new communications equipment, an entire battalion made ready to re-take Dauper village.

As the force was about to leave, they started hearing large explosions and rapid gunfire from too far away to even see, indicating that the weapons being used were on a far larger scale than anyone in this military were accustomed to. The sounds seemed to have been coming from the south, which made everyone think that the battle had already begun

"Thank god someone is already there." Sasha said to herself, feeling somewhat steeled in knowing the fight they were about to bring to the titans.

Mikasa looked at Sasha, who produced a baked potato (probably stolen from the kitchen) from her pack and began to eat. "You might want to save some of that for the road." Mikasa stated.

Sasha hurriedly gulped down the bite of potato she had just taken. "Don't worry, I have more." She said. "I'll share."

Mikasa cracked a smile and asked Sasha a quick question. "Would you be willing to share that potato? Maybe...half?"

Sasha broke off a little more than a quarter of her potato and handed it to Mikasa, with whom she didn't mind sharing anything, especially since they were an item. Mikasa chuckled at her girlfriend's offer, but accepted it anyway.

…

Orders came down from the top and the force started making their trek to the southern district. Nobody had an idea of what would be in store for them as they moved out, aside from the obvious that the titans were tough, but now more manageable due to the military gear now in tow.

As the force came closer to the southern district, the sounds of explosions seemed to grow in intensity and frequency. The telltale whistling sound that mortar shells make was coming from the more mountainous and hilly areas, which is no surprise, as standard artillery sometimes requires line-of-sight, but would be blocked or inaccessible to standard artillery. The sounds were still a mystery to the re-take battalion, as they were unaware of any other units who could have been in the area before them. They were still welcomed, though, as the titans were not intelligent and would not be able to use artillery, meaning the reports were coming from human weapons.

Commander Pixis radioed the tank squadron to load APFSDS (Armor Piercing, Fin Stabilized, Discarding Sabot) rounds to fire on the titans as soon as they came into view. "The new software should let you zero in on the weak spot." He said. "The hardened spikes should easily take their heads off."

Eren was in one of the new OCO-130-A tanks, equipped with a rather large 130mm cannon and an autoloader system. He flipped the switch to make the system load the APFSDS rounds from the hull, instead of the HEATT (High Explosive, Anti-Tank/Titan) rounds. "Oscar One Bravo, loaded." He called over the radio, as other tanks started calling in the same.

Sasha was a keen huntress, with sharp eyes. As would be expected, she was assigned point detail, heading up before the tanks to call contacts for the tanks to fire at. As she peered through the scope, she saw a titan clumsily make a right turn towards her position. She jumped slightly, then remembered she was too far away for the titan to be a threat to her just yet. "Sword One Charlie checking in, titan at grid one- seven foxtrot, X-ray two, Yankee eight, over." She called in.

Eren heard the call first and reacted. He raised the tank's gun to aim at the weak spot on the neck. Although he could not see it because he was facing the titan. He knew the rounds he was ordered to use would penetrate far enough, though. "Oscar One Bravo, firing on target." He called.

The cannon fired, which made a deafening sound. The sabot peeled off and the round flew down range to find its mark. The depleted uranium spike bored through the titan's neck, ripping flesh off as it blew out the back. The titan didn't even seem to flinch as it fell to the ground. "No reflex kill, excellent shot, Oscar One Bravo." Pixis called over the radio.

The battle continued rather smoothly, until Connie called one contact nobody would have expected, or wanted to hear. "Sword Five Delta, checking in. I have eyes on the armored titan, charging to position at grid One-Seven Foxtrot, X-ray Two, Yankee Seven, headed east."

Everyone's heart sank, as they knew the armored titan was simply too fast for even the newest tanks to pan to shoot at, and it would soon be on Eren's position. The armored titan leaped over a small house, and to everyone's surprise, the armored titan was hit hard by something, which knocked it over, also blowing several plates of armor, one arm and a large portion of the right side of the upper torso off of the titan. Then, a split second later came a thundering ballistic crack, followed by a massive gust of wind.

Sasha peered through her scope to try and see what could have done this. She saw what looked like a mechanized titan in the crosshairs. She could feel the hair on the back of her neck standing up. "S-sword One ch-Charlie, umm... there is a..." Sasha called over the radio, not sure of what to say. "Well, I can't really describe it, but it looks like some other form of... mechanized titan. But it looks different, over."

"Eyes on target, round loaded." Came from Eren. "Oscar One Bravo, ready... wait" Eren stopped as some sort of electronic interference started to distort the picture in his viewfinder. "Firing on target." He said, as the distortion seemed to have stopped.

The 130mm gun fired another APFSDS round, which shouldn't have caused the viewfinder to jar around due to the advanced fire control systems. However, the screen flickered and was off of Eren's selected target, which was one of the legs. The spike instead hit the ground behind the unexplained bipedal target to the front. "Oscar One Bravo, round missed." Eren called in. "Reporting suspected software or hardware malfunction, over."

After a moment of silence, a static laden, indistinct transmission came over the radio. After a moment, the static faded and transmission was again clear. "Oscar One Bravo, repeat transmission." Pixis called out.

"Sir, there was some sort of glitch or malfunction, the gun missed target by 1 meter low, 2.5 meters to the right about 100 meters range." Eren called back.

All radio transmissions stopped for a moment, then, a deep, almost scary voice came over the radio. "Kid, I'm not a titan." He started. "I cannot guarantee your safety if you try that again. I mean, you did see what I just did to that titan over there, right?"

The voice made everyone pause momentarily. "That distortion was Rex's PCMS, or Projectile Counter Measure System." The voice continued. "None of the tanks or cannons you have can hit me. Besides, we're fighting a common enemy here."

The machine, unofficially named "Metal Gear Rex", often shortened to simply "Rex", turned down a road and rapid, thundering gunfire could be seen, heard and felt in the vicinity of the road. Connie saw what Rex was shooting at, which was a group of smaller titans, all of which were flying apart as the 30mm GAU-8 Gatling guns spat out 10 pound depleted uranium anti-tank cells at a horrendous rate. "Sword Five Delta checking in, the umm... mechanized unit is successfully engaging a group of titans, over." Connie called.

Everyone was somewhat relieved to hear that this machine appeared to be on their side.