Alpharius: Alpharius was the last of the Primarchs to be discovered, and by this time, The Great Crusade to regain the Imperium was underway, and the Emperor's time was occupied with the strains and tasks of ruling his new empire.
This ultimately meant that Alpharius spent very little time beyond an initial meeting with the Emperor, as the Great Crusade was well underway by then and the Alpha Legion was needed on the Eastern Fringes. This had a serious impact on his relationship with the Master of Mankind, and Alpharius came to respect and admire Horus more than the Emperor, whom he saw as distant and uninterested.
Alpharius and the Warmaster met when the Luna Wolves, exploring the Eastern Fringe, were attacked by a small group of starfighters. Although primitive in comparison to the craft of the Imperium, the fighters were well-led and retreated, luring the Wolves into a minefield. A small boarding party even managed to gain entry to a scoutship, and stormed its bridge. Horus himself shot down 4 of the 5 men who stormed the bridge; the fifth dodged his bolter shell. He advanced under a hail of fire, which slowed, but did not stop him. It was only when he closed to the point of having his hands about Horus' throat that he and the Warmaster recognised their commonality.
Alpharius was a skilled tactitian, and a keen believer in the independence of his troops from him. While many of the Primarchs led through force of personality and by heroic example, Alpharius believed that his soldiers should be able to function without him and he regularly conducted exercise to build and test this skill. He would frequently be absent from battle, so that Alpha Legion units became independent and not reliant on his leadership alone.
These unorthodox methods, and his equally unorthodox tactics, drew him a great deal of criticism from the more traditional Primarchs; particularly Roboute Gulliman, author of the Codex Astartes. One case in especial drew Alpharius flak from Gulliman; Tesstra Prime. The world was vast and well equipped. Alpharius delayed his landing by a week, planning. This gave the Tesstrans time to dig in and fortify their positions, and it was believed that over a million soldiers awaited the Legion on their landing. But Alpharius' delay had allowed time for his infiltrators to conduct vital operations behind enemy lines, and when the Legion attacked, they concentarted their forces on one point in the defences, which they knew would be isolated as they assaulted; transport and supply links severed by demolition charges and sabotage set in place days earlier. The Tesstrans surrendered a week later. Gulliman berated Alpharius for his delay, questioning why he did not attack when the Tesstrans had been unprepared, to which he responded; "That would have been too easy."
It was this sense of martial pride, combined with his closer relationship with Horus, that ultimately led to Alpharius siding with the Warmaster during the Heresy. Historians believe that the Alpha Legion Primarch was even the one responsible for the plan of the trap at Istvaan V. It remains impossible to tell exactly how far Alpharius fell to Chaos; the Legion is certainly tainted and heretic, but seems to be less corrupted by Chaos than the other Traitor Legions, and has no patron and no home in the Eye of Terror. Alpharius himself appears to have been motivated mainly by a simmering jealousy and stung pride; after the Istvaan Massacre, the Alpha Legion did not follow the other Traitors to Terra, but struck against other Space Marines; determined to prove their superiority. Even after the Warmaster's death, this campaign continued, until the Alpha Legion came into direct conflict with Gulliman and the Ultramarines on Eskrador.
Gulliman's plan was to lure Alpharius into single combat, and thence to mop up the demoralised and leaderless Alpha Legion. The first part of his plan succeeded; Alpharius fell to Roboute in a titanic fight in the Alpha Legion camp. But the Legion was not reliant on Alpharius, and the Ultramarines battled for a further two weeks before abandoning Eskrador and the Alpha Legion.
Source: Codex: Space Marines, 3rd Edition by various, Codex: Chaos, 2nd Edition by various, Codex: Chaos Space Marines, 3rd Edition by various
Submitter: Simguinus
Hive World Terra