A/N: Relevant notes will be at the end of the chapter.

-000-

It has been over 300 years since mankind first left the cradle of Earth. In space, mankind recreated their homeworld in hundreds of gigantic space colonies, later in other planets, then around other stars.

The Solar Sphere Congress, the constitutional republic which governs mankind and its colonies, has spread into dozens of other star systems surrounding Sol thanks to the discovery of ancient interstellar transportation devices called "Mass Relays".

It is now Universal Century 0379. Unbeknownst to all, mankind's expansion into the stars has invisibly lead it to an unavoidable collision course, one which will change the fate of all. For humanity... and everyone else.

-000-

Mobile Suit/Mass Effect

Episode 1:

Encounters in Space

-000-

"You ever think anyone's out there?" I asked.

I was standing on the front observation deck, watching as our Chariot Class Cruiser - the CSS Risima - approached a dormant Mass Relay.

"Sometimes." My friend answered bluntly, though his voice was devoid of the usual charisma he normally had. It was instead filled with what sounded like... nervousness?

I turned to him and frowned a little. He was 6'2, with a messy mop of medium length blonde hair that ran to the nape of his neck. Smoky tinted goggles covered his eyes, a necessity due to a long running medical condition of his. He wore a blue and green Congressional Space Force officer's uniform, with the bars on his shoulders and collar signifying he was a Lieutenant. He was my equal in rank, though not in height. I sometimes found this difference annoying, and whenever my friend was in the mood he would always rub it in.

Back to the conversation, he wasn't usually this moody or quiet. Something was off.

"You're awfully quiet today, Verns." I told him. "Migraines again?"

"No..." He said. "It's something else... like alarms ringing in my head telling me something's coming."

"Like what?"

"I don't know." He shook his head. "But my instincts are telling me it's nothing good."

"Lieutenant Hedder and Kreusgluck to CIC." The ship's PA suddenly called out. "I repeat, Lieutenant Hedder and Kreusgluck to CIC."

I raised an eyebrow at that.

"This can't be a coincidence." I said.

"Let's hope it is." Verns said, pushing off the wall and grabbing on to the friction track leading to the CIC. "Come, Irena. Best not to keep Captain Koda waiting."

"Yeah." I agreed.

I took one last look at the still dormant Mass Relay and sighed. Guess I was going to miss watching this one power up.

-000-

Verns and I arrived in the CIC a couple of minutes after. Before we entered, I made sure to straighten my uniform and tie my long silver hair into a bun. Captain Koda wasn't the strictest officer I'd ever served with, but he has chastised other crew members for not keeping up uniform and appearance standards. Seeing as I'd rather stay on his good side, I made sure to keep myself looking like a model officer in the Space Force.

The mechanical doors to the CIC opened with a mechanical hiss. Inside were a hive of screens, terminals, and other such stations. Verns and I floated ourselves to the central projector - a massive holographic screen that combined all the various outputs of all the terminals in the room for the benefit of whoever was in charge. Captain Itami Koda was attentively watching the projector. He was an older man, with wrinkles on his face and grey streaks growing on his sideburns. The man wasn't tall, and he was quite rotund around the waist. Beside him was Lieutenant Dera Bullow - the new XO of the Risima. Bullow was a transfer from a different ship. She was tall, almost as tall as Verns was. Her blue locks of hair accentuated her dark grey eyes. I hadn't been able to get to know her much, but she seems to prefer to keep to herself.

"Captain." Verns called out as he stopped his floating by grabbing onto a nearby railing. He then caught me and pulled me beside him.

"Lieutenant Hedder." The aged, portly Captain Koda nodded to Verns. "Both your, and Lieutenant Kreusgluck's mobile suit teams are to be on standby."

"Standby?" I asked.

"Yes, Warrant Officer Malcolm said he's detecting faint readings on the deep wave sensors. He thinks they're comms chatter of some sort."

"Do we know who the chatter is coming from?" Verns now asked.

The captain was pensive at first, but then answered my friend's question.

"That's the issue... we don't know who's sending out the chatter, or what kind of chatter it is, for that matter." Koda told us. "All we're picking up is chatter echoes being caught by the Relay."

I furrowed my brows at that.

"How is that possible?" I said. "The Relay is still inactive. Even if some Separatists managed to jump through and deactivate it from the other side, Shanxi Control would've detected it."

"Again, Lieutenant, we don't know." The captain reiterated. "Which is why you and Lieutenant Hedder will be on combat standby. We don't know what's waiting for us... if anything is waiting for us on the other side, so let's not take any chances."

I gulped.

No, this can't be a coincidence.

-000-

Captain Herac Magarius watched his subordinate fidget with his claws as he explained the situation. It was honestly a rather pathetic display of character, unfit for a member of the proud Turian Navy.

"Relay 314... it- it's gone active, sir." The subordinate said.

Spirits, he looked so young, probably fresh from training.

Magarius shook his head. This assignment to the hind's end of nowhere was really going to drive him insane... but at least there was a silver lining now.

Relay 314 was active! That meant somebody from the other side was coming through. Since no Council expedition had ever been through 314, it stands to reason that this was a new alien race.

First contact was right around the corner. If Herac played his cards right, this was his one way ticket out of this stupid post.

"Very well." Herac said. "Report this activity to Sector Command, and request a welcoming party be deployed. Otherwise, keep monitoring the situation."

Yes. This was Herac's chance to rise above his station. Those fools in Sector Command will rue the day they sent him here as punishment for questioning their authority.

-000-

"Risima has exited relay transit. All hands to Readiness Condition 2." The ship's PA blared out.

I zipped up my normal suit and floated myself through the door and into the Starboard hangar, where my mobile suit team was based from. Verns' team was on the Portside hangar. I caught the railing of the observation platform close to the door, then kicked off it towards my mobile suit.

It was a mass production machine. An M-18-F Gunstrike F, which was the commander variant of the more common M-18-E Gunstrike E. The variances in performance were minimal, with the biggest difference being the extra antennas mounted on the side of the head for command and long range communications. It was a fairly fancy and advanced design, for a machine that was relatively cheap to produce. Long gone are the harsh, boxy shapes of 1st generation of mobiles suits from 300 years ago. This one was sleek, with curves and angles flowing naturally. Gunstrikes were usually painted in a white and dark green color scheme, team colors not withstanding.

There were 3 Gunstrikes on my team, each with a blue stripe painted across the left 'bicep' and 'thigh' armor. We were Blue Team to Verns' Red Team, who had a long red line going down the right shoulderpiece and through the head unit's crest like a mohawk.

"Lieutenant, your mobile suit is just about loaded and ready for operations." One of the ship's mechanics reported.

"Thanks, Derrick." I said, giving him a fist bump as I floated by him towards the suit's cockpit hatch.

I grabbed onto the hatch and swung myself inside. With a single fluid and practiced motion, I spun myself around and landed perfectly on the cockpit seat. I congratulated myself a little for pulling that off, then went about going through my machine's pre-launch checks.

"Power plant okay, joint servos okay, weapon systems okay, thrusters at nominal output... green across the board."

I put on my helmet, then connected my normal suit's communicator to the mobile suit's own comm system. My helmet's HUD synced with the mobile suit's panoramic display cockpit in an instant and I was now linked to the battle network.

On the display, she saw the Risima and the two Curran Class Destroyers - the CSS Otto Gleiswick and the CSS Montgomery Oum - were marked in dark green. Friendly mobile suits like Blue 2 and 3, Verns' Red Team, as well as Green and Gold teams from the Destroyers were highlighted in light green. Unidentified units will be tagged yellow, while confirmed hostiles in red.

I turned my Gunstrike's head left to right. Blue 2 and 3 were properly tagged in light green, so the IFF was working fine. Good. Considering nobody really understood what we were potentially up against, being able to easily tell friend from foe is a real blessing.

Once I had confirmed the IFF was functioning perfectly, I took a step forward with the mobile suit, away from the scaffolding and towards the weapon rack. I took my usual loadout. Beam Rifle, Beam Saber, and a shield. Not an exotic setup, to be sure, but I quite preferred having something simple but reliable than something flashy but finicky to work.

With that out of the way, I moved my mobile suit right to the catapult. If anything happened, I'd be the first to go.

"Irena Kreusgluck, Blue 1, now on standby!" I announced.

-000-

It had been four and a half hours since their patrol had been retasked to meet what was supposedly a new alien race. Commodore Uriah Trevanian was on edge. There was an immense amount of pressure riding on his shoulders. A part of him was giddy to meet this new race, while another was crumbling with anxiety at the thought of meeting them. It was horrid. It took all his training and experience to maintain perfect composure.

His crew needed to know that their leader knew what he was doing, and that he could handle the situation just fine.

"Sir, we're exiting relay transit shortly." The helmsman reported.

"Excellent." Uriah nodded. "Once we're in the system, get in touch with the watchpoint and have them update us with everything they've picked up while monitoring these new aliens."

Once Uriah's cruiser - the PFS Galateus - entered the star system proper, their comms officer quickly linked up with the watchpoint and quickly received an intel package containing everything that these new aliens were doing. The results were... concerning.

The Commodore furrowed his browplates as he read the report. These aliens had something different about their ships. Eezo based ships normally emitted a very discernible, very specific energy signature. This energy signature was what made picking them out from the rest of the random noise and interference in space easy. The ships that these aliens used were emitting something else. While the Turians could read faint Eezo emissions from the aliens, it was bathed and surrounded by some sort of radiation that seemed to act like a thick, difficult to penetrate fog. Both Uriah's small warship squadron and the watchpoint had trouble pinpointing just about anything when it comes to these new aliens. The only thing they've been able to tell is that there's at least more than two of their ships, and that they're on the move.

"Track their movements." Uriah ordered. "Where are they going?"

"Stand by, VI is calculating possible trajectories." A sensors officer said.

The holographic display in front of the command podium lit up with a map of the star system. 6 yellow blips represented Uriah's patrol squadron of 1 cruiser and 5 frigates. A green blip stood in for the watchpoint that had alerted them in the first place. Finally, the alien ships were shown in the form of a single blue box, due to the lack of specificity on what they are exactly.

After a few short seconds, a series of lines were drawn from the blue box charting its potential course.

Given the just under FTL speeds they've been cruising at for the past few hours, the points of interest around the star system, and the proximity of the item in question to the alien contacts, Uriah shouldn't have been too surprised... but he was taken aback regardless.

The VI predicted that the contacts were trying to reactivate the still dormant relay.

Uriah's eyes widened at that revelation, before narrowing in focus.

Were these aliens trying to reactivate Relay 313? That can't be allowed to happen. Citadel Council regulations forbids it for good reason. There's no telling what sits on the other side of that relay. Could be another Rachni or Krogan War waiting to happen.

The aliens were a few minutes away from reaching the relay... there really was no other possibility.

That does it. The squadron would have to close in and intercept.

Uriah spoke to his comms officer.

"Order the frigates to assume a claw formation." He said. "We're closing the gap."

"At once, Commodore."

-000-

"Sir, the contacts are accelerating... they're on a course to intercept." I heard someone on the battle network report with a stressed tone of voice. "They're... I don't believe it! They're fast! Estimated contact time is currently 14 minutes."

Our little flotilla had spent the past few hours surveying the system and was extremely close to the dormant relay. At our current cruising speed, reaching there would only be another five or so minutes. Full reactivation of the relay would take around fifteen minutes.

That these ship contacts could somehow move at such speeds implies a lot of things.

The first is that these guys weren't some Separatist Warband. The Separatists couldn't have developed so many warships capable of such FTL speeds, especially not when their mastery of Element Zero was eclipsed by the Congressional Space Force.

I gulped. They weren't Separatists, and they sure as hell aren't with the Solar Congress... so does that mean they're aliens? Was humanity not alone after all? A dozen more questions buzzed in my mind, but I stowed them at the back of my mind... for now. There would be a time for all of this later.

"Do we know what they are?" I asked in the battle network.

"Six ships... no Minovsky particle reading... my God, look at the size of that thing... by our tonnage, it looks like they have four- no, five cruisers and one battleship."

A pit formed in my gut.

Five cruisers AND a battleship for an intercept mission? These guys were dangerous, and they had the resources to spare. I gripped my control sticks tighter.

"Captain," Verns then spoke on the network. "Our orders?"

"Maintain Readiness Condition 2 and proceed with the current Relay inspection, for now." Captain Koda answered. "We don't know what they're going to do, or what they're capable of. Let's play our cards close to our chest and keep on the current mission... but if worst comes to pass, Red and Blue team will launch and do what damage you can do to slow the enemy fleet. Green and Gold will stay behind for fleet defense. We'll turn about and go full burn for the Relay we came from."

"Aye sir." I answered.

-000-

"We're approaching the alien contacts... 5 minutes out." The Galateus' helmsman reported.

"Excellent." Commodore Trevanian nodded. "Update on hail attempts?"

"No bites so far." The comms officer reported.

"Keep trying." The Commodore ordered. "Stopping them from activating the relay takes precedent over anything else!"

The Galateus and its squadron sped onwards, steadily closing the gap on the alien ships. As the distance between the two groups evaporated, the sensors on the Turian ships were finally able to get a good read on the unknown formation.

"Sir, alien ships are... two frigates and... one light cruiser!" A sensors officer reported.

"A small formation." Trevanian mused to himself.

Not just a small formation, but smaller ships as well. By Citadel tonnage standards, these would barely qualify for their tonnages.

"Do we know anything about how those ships are emitting that radiation?" The captain asked.

"Our sensors can't identify it." The sensors officer answered. "It's... it's like nothing we've ever seen. Energy readings are also all over the place. We're not sure what it does."

Trevanian clenched his fringes. This wasn't at all like the other first contacts in history. The technological divergence was too much to be predictable. There were too much unknown variables at play.

"Commodore, we're now within visual range!"

"Good, start flashing them down. Get their attention, stop them from approaching the Relay!"

A small hatch on the Galateus' topside opened, revealing a turret with a powerful signal light on it. The light flashed in a rapid rate, its operator hoping against all hope that it would catch the aliens attention.

"S-sir!" One of the sensors officers suddenly called for attention. "The alien contacts have reached the relay and initiated reactivation!"

The growing pit in Uriah's gut had transformed into a blackhole. His mind raced, yelling at him to act NOW.

"Increase cruising speed." He ordered. "Continue trying to hail them... but if they still refuse to respond, then we will have to take drastic action."

A tense silence now filled the bridge.

Drastic action... everybody knew what that meant.

Nobody wanted it to come to that.

-000-

"Lieutenant Bullow... do those holes in front of their ships look like the end of a barrel to you?"

Dera squinted as she observed the camera feed of the approaching alien ships. As someone who specialized in intelligence, She was trained in the methods of identifying and classifying ships based on appearance alone. Judging by the large, avian like design of the alien ship and the pronounced hump running from the ship's stern to bow, the XO surmised that the ship's main weapon was a sort of large spinal cannon. Along with the inverse delta formation the enemy fleet had, she could predict their plan of attack.

"It appears that their ships rely on a spinal mounted weapon of some sort." Dera shared her thoughts. "Given their formation, their plan of attack is likely to envelop us from the front and rear."

Captain Koda stroked his beard as he observed the tactical map.

"I'm in agreement with your assessment." He said. "What do you suggest we do?"

"Sir?" Dera asked for clarification, unsure why the Captain was asking what she specifically would do for their next course of action.

When the Captain didn't budge, she cleared her throat, analyzed the situation in more detail for a moment, then finally answered.

"Given the precarious situation... if these contacts open hostilities, we should turn hard to starboard, away from the enemy fleet. Our ships should fall into a battle line formation immediately, then follow... this course back towards the Shanxi-Fumitan relay."

Koda looked to the screen, inspected the route that Dera had chosen, then looked back at the Lieutenant.

"Through the asteroid cluster?" The captain asked.

"Since they seem to rely on a spinal mounted primary weapon, going through the asteroid cluster will limit both their angles of attack in addition to neutralizing their numbers advantage." Dera explained. "Meanwhile, our turreted hyperbeam cannons can engage targets with far more flexibility. Of course our Mobile Suits are also agile enough to weave between the asteroids to harass the enemy."

The Captain regarded Dera's words carefully as he kept analyzing the map.

"Your advice is sound, Lieutenant Bullow." Koda finally said. "Have this transmitted to the Monty and Gleiswick at once. We can't have them falling behind on this plan, after all."

Several more minutes passed, each passing minute seemingly more tense than the one previous. The gap between these newly found aliens and themselves were closing. Dera watched on the holographic monitor as the alien formation -an inverted wedge formation with the Battleship taking the central position- began to loosen up, spreading out slowly.

They were beginning their envelopment. There was no question about it. Captain Koda saw the move too.

"All hands, assume Readiness Condition 3!" He quickly ordered. "Power up all weapons and begin dispersing Minovsky Particles at full combat density!"

-000-

"Commodore! Radiation spike detected coming from the alien ships... energy readings beginning to climb as well!"

"Have they responded to our hails yet?" The Turian Commodore quickly asked. His decision will depend entirely on the answer he receives.

The comms officer knows this. He hesitates to answer, hoping against all hope that these aliens responded to their hails.

One second... two seconds... three... five... ten... no answer.

"No... No response from the alien vessels... sir." The comms officer regrettably reports.

Trevanian finally let go of a breath he didn't realize he was holding. All bets were off the table now. With a deep sigh, he steeled himself with grim resolve.

"The alien contacts have regrettably refused to respond to any of our attempts to communicate with them, to stop them from reactivating a Mass Relay without proper Council authorization." He began. "To ensure the safety of all our people, the 47th Patrol Squadron will commence policing action in accordance to the Citadel Council Stellar Regulations. Let the records show that we have made every possible attempts to dissuade these aliens from their reckless cause."

The die is cast.

-000-

Relevant Notes:

History and Timeline: I haven't fully mapped out the timeline yet, but assume all the mainline UC entries from Gundam '79 up until G-Saviour are cannon. UC Side-Story Manga canonicity is super iffy so I'm still sorting out which ones are canon to this fic and which ones aren't.

Ship size discrepancy: UC Gundam ship sizes are significantly smaller than their Mass Effect counterparts. The Dogosse Gier battleships, flagships of the Earth Federation fleets, are only 630 meters long. 600 meters doesn't even come close to the Cruiser/Dreadnought threshold. There aren't any concrete classifications for UC ship tonnages, or at least none I can find in english, so I have to make up quite a bit to compensate.

A/N: This will be a relatively short story. I'm only planning 12-16 chapters, focusing entirely on the First Contact War. Folks that know me from Mass Effect: The Great War can rest assured I'm not ditching that fic for this one.