First Rachni War

Previous:	Rannochian Civil War
Concurrent:	Fifth Reconciliation Neverending Night
Next:	Second Rachni War
War of Relay 628 Part of the Rachni Wars
Date:	29 January 1 CE - 6 May 5 CE (4 years, 3 months and 8 days)
Location:	Far eastern Inner Council space / Milky Way Galaxy Southwestern Rachni space / Milky Way Galaxy
Outcome:	Major Rachni victory Beginning of the Rachni Wars Salarian Union outer colonies left devastated First contact between salarians and the rachni ends in disaster Salarians deactivate Relay 627 in an attempt to prevent further rachni incursions Salarian expeditions pushed out of rachni space
Engagements:	Massacre at Relay 628 Skirmish at Relay 628 First Battle of Iera Battles of Horizon (1-2) Relay 628 counteroffensive Battle of Utukku Skirmish over Inakhos First Battle of Kashshaptu Second Battle of Kashshaptu Battles of Horizon (3-4) Fall of Horizon Bombardment of Utukku Battle over Suen Battles of Mulla Xul Slaughter on Watchman Second Battle of Iera Iera Containment Zone Relay 627 defensive operation Six Days of Fire Battle of Almarcrux Destruction of the Salarian Armada Final Battle over Relay 627
Belligerents Salarian Union First Rachni Collective Commanders Aepin Oyore † Todarth Nozom Jodan Nexa † Maedarth Ilbeni Rurik Rinmorne † Waerlar Haessi † Symphonic Exalted Cacophonic Symbiont Coloured Melody Strength Union Army 2 million troops 2,000 support aircraft Union Navy First Fleet 278 ships Fifth Fleet 121 ships Sixth Fleet 103 ships Seventh Fleet 94 ships Special Tasks Group 700,000 armed personnel 240,000 intelligence agents 12 million rachni workers 9 million rachni soldiers 16,000 brood warriors 13 rachni queens 300 ships Casualties 374,000 army troops killed 800 aircraft destroyed 135 ships destroyed 200,000 total STG personnel killed 4.5 million civilians killed Roughly 45,000 total rachni killed 9 ships destroyed

"The first conflict the Council ever fought. We had enjoyed centuries of peace, but in our efforts to explore the galaxy and welcome more into our new galactic community, we had forgotten the possibility that not all races had such noble intentions. Our ancestors must have only realized the full extent of their mistake when the dust cleared from the first, devastating rachni invasions."

— A salarian teacher on the First Rachni War.

The First Rachni War, also known as the War of Relay 628 historically and sometimes as the Salarian-Rachni War, was a major conflict between the Salarian Union and the First Rachni Collective fought between 29 January 1 CE to 6 May 5 CE that kickstarted the Rachni Wars. In 500 BCE, the asari and salarians founded the Citadel Council, and from that point forward began to expand their territory at a massive rate, with the Asari Republics rapidly claiming territory to the north, while the Salarian Union was left to extend its reach to the far east. Expansion between the races was unchecked, with both sides eager to not only explore, but hopefully come into contact with new species, which they hoped to welcome into their new galactic community as members of the Council. In late 2 BCE, the salarians began their final far eastern territorial push, where the Salarian Union would reach its greatest territorial extent, having colonized an unprecedented amount of new worlds. A expedition was sent through what the salarians dubbed Relay 627 in early 1 CE, which linked to another a relay known as Relay 628: eager to explore, this small expedition, made up of three civilian scientific vessels, activated Relay 627 and went through: after one transmission to Sur'Kesh and the Citadel confirming they had exited on the other side, they were never heard from again. In response, a second expedition, this time escorted by warships, was sent through the same relay, where they discovered the fate of the expedition: they had made first contact with the rachni, and been swiftly slaughtered. The second expedition suffered the same fate, although one warship managed to limp through the relay and alert the rest of the Union. Thus began the First Rachni War.

Compared to the next three conflicts of the Rachni Wars, the First Rachni War was rather small-scale. The salarians wished to keep the war a secret from their new asari partners, not wanting to compromise their partnership, and elected to fight it alone. The rachni gave no reason for why they launched an unprovoked attack on the salarian expeditions, although many sympathetic historians argue that, from the rachni perspective, they may have seen the salarian explorers as a precursor to invasion, and had acted pre-emptively to defend themselves. Regardless of who was to blame, the rachni response was brutal: they launched entire fleets through Relay 627 to assault and sack nearby salarian colonies in a back-and-forth battle for supremacy over the region. The salarians would respond with their own punitive counterattacks, but these proved ineffective against rachni colonies when it was discovered their hives were underground, and thus protected against orbital bombardment. The war was largely fought in space until the next year of the war, when the rachni began landing troops to attack salarian worlds. It was here the salarians learned they were no match for the rachni, with their weaker, less numerous troops being overwhelmed by the swarms of rachni insects that were stronger and more ferocious. Salarian attempts to land troops on rachni worlds were met with the same results, with entire battalions being wiped out in minutes. This back-and-forth struggle continued for years, until the rachni seemed to finally pull back. The salarians believed the rachni had withdrawn, and had elected to have Relay 627 sealed off and guarded by the Union Navy. In reality, the First Rachni War had been seen as little more than a large-scale reconnaissance mission by the rachni to assess the strength of their enemy. The real invasion had yet to begin.

The First Rachni War was the ultimate nightmare scenario for a first contact. It ended in complete disaster for the salarians, who not only suffered a substantial military defeat, but had been subjected to ruthless and pointless slaughter for reasons they couldn't, at the time, understand. First contact protocols would be heavily reformed after the incident, and would eventually lead to the Reckless Relay Activation Countermeasure Act (54) some fifty years later.