Their first destination was the Achaemenid Empire, as it was the closest. It was a nation-state comprised of several “wealthy tribes” that coexisted with each other with little issue. The Emperor and His army encountered no resistance as they marched through the streets of whatever tribe they came across before reaching what could’ve been described as their capital as it was used for meetings by the tribe leaders. When the Emperor told them of His plans for humanity, they were very quick to join Him and proclaimed that all their resources were His. As a form of thanks for their loyalty, the Emperor promised them a seat of power within the Imperium once the War of Unification was over, but didn’t mention that it was only if they survived until then.
Since the Achaemenid Empire wasn’t conquered through force and was perhaps the most peaceful place on Terra at the time, they were spared from the horrors of atomic war and invasion from the Emperor’s superior army of genetically-engineered soldiers had they resisted. In addition, the genomes of the nation-state’s citizens were uncontaminated with any inherent flaws and genetic defects that plagued near all other nation-states over Terra from lingering radiation and biological warfare vectors. This made them good candidates for recruitment into the Space Marine Legions, specifically the XV Legion, named the Thousand Sons by the Emperor Himself.
The next destination was Albia. Sometimes referred to as Old Albia, it was a nation-state that bordered Northern Atlan and was known for its ancient warlike clans, the regions of Albia consisting of towering, soot-blackened castram-cities. Under the rule of the Unspeakable King, Albia frequently clashed with the Pan-Pacific Empire until they were aided by the Emperor and His forces, among them the Stormbird from the Yndonesic Bloc after its people rebelled against their ruler -- Cardinal Tang, the “Ethnarch” -- and joined the Emperor at the promise of a better, kinder regime. Taking direct command of His army, the Emperor decided to test the skills of Tara and Ashleigh by sending them ahead to face the Pan-Pacific Empire’s leader. Somewhat hesitant at first, the two transhuman women obeyed their Lord and set about the task He’d given them.
After days of carving through droves of enemies, the two former ponies finally confronted Narthan Dume, the Tyrant of the Pan-Pacific Empire, a man regarded as being a “half-mad/half-genius” and the most infamous of all the tyrannical rulers that dominated Terra. Outsmarting whatever traps or tricks he attempted and outmatching him in combat through their teamwork, skill and determination, Tara and Ashleigh were able to defeat Narthan Dume and remove him from power. Dume’s defeat resulted in the combined forces of Albia and the Emperor’s army in dominating the Pan-Pacific Empire’s own army and its absorption into the Imperium of Man. The people of the Empire celebrated their freedom from Dume’s oppression, the tyrant himself set to be imprisoned within Khangba Marwu - also known as The Vault - but urging by Constantin Valdor, the Captain-General of the Legio Custodes, had the tyrant executed and his lieutenants being incarcerated in The Vault in his stead.
Afterwards, however, the Albians refused to kneel to the Emperor despite Him aiding them, and so met His army of Thunder Warriors with their own proto-Dreadnaughts and armoured soldiers from their Ironside Clan. Battle after battle, the Albians managed to hold off the Emperor’s forces, but at a staggering cost to their own. Although this presented a considerable challenge for the Emperor and His forces, He was nonetheless impressed with their determined and brutal resistance, and sought to end the fighting and take Albia through diplomatic means. He admitted to the martial temper and indomitable spirit of His foe and called for a cease-fire. When the Albian Clan Lords agreed to the cease-fire, the Emperor, Tara and Ashleigh came before them unarmed wearing white and crimson robes. The Emperor spoke of His vision for a unified Humanity, and offered them glory amongst the stars and redemption for the past conflict. After discussion amongst themselves, the warlords of Albia shocked many of their people when they agreed to the Emperor’s terms, declaring that He was different from past tyrants, and became some of His most zealous followers throughout the rest of the Unification Wars.
With Albia now under His sovereignty, the Emperor saw the Albians as suitable recruits for the XIV Legion, who would name themselves the Dusk Raiders. So suitable were the warriors of Albia for induction into Space Marines, recruits drawn from the various castram-cities and Ironside Clans were also incorporated into the VIII and X Legions, though they did not use them as much as the XIV Legion.
Boeotia was a nation-state that fought against full Unification for a considerable amount of time. Despite the government of Boeotia tactically recognising the Emperor’s dominance over the rest of Terra, the ruling monarchy used all manner of diplomacy to avoid losing power. In a show of patience and benevolence, the Emperor allowed the ruling dynasty of Boeotia -- the Yeselti -- to carry on in a semi-autonomous state with the intention that they would eventually integrate into the Imperial Terran government at their own speeds, and with as much dignity as possible.
Instead, however, the Yeselti tightly clung to their independence for over 150 standard years until the Emperor seemingly grew tired of waiting and ordered the Imperial Army and Thousand Sons to invade the province and crush the rebellious state, under the command of Tara Astrum. Boeotia was known for possessing a relatively large concentration of industry within its borders and for the existence of an ancient yet buried shrine from a previous age. And it is in this shrine where they made a discovery.
The Emperor’s forces were not idle during this century and a half and continued the Unification Wars, conquering more and more nation-states. Those conquered and absorbed into the Imperium of Man during this time were either small or had nothing unique that made them more than a footnote, such as Britonnica, Europa, Gyptus and Jermani. Albyon only stood out for being ruled by the tyrant Uilleam the Red, who was defeated and imprisoned within the dungeons of Khangba Marwu, The Vault. Merica was a large nation-state located on the Nord Merican continent and was mostly comprised of hive cities. The Skandians were nothing more than a sizable band of raiders that repeatedly attacked Europa in pursuit of plunder, and were exterminated at the Emperor’s command when they refused to accept Unification.
The nation-state of Franc was initially conquered at some time just before Boeotia, but its last independent ruler, Havuleq D’agross, lead a rebellion against Imperial rule and killed the Emperor’s appointed territorial governor. He began his rebellion in the city of Avelroi, his influence rapidly spreading until he could amass a force of 50,000 rebels due to the fact that the Frank, the name the people were known by, did not take kindly to invaders even before the Unification, though they were largely unskilled militia. They eventually fought against the Emperor’s at what would be called the Battle of Gaduare, a line of high hills by the ruins of the Guaduare Bastion, only to be wiped out by a force of no less than 5,000 Imperial troops led by Ashleigh Arcus, including Space Marines from an early generation of the Dusk Raiders Legion.