Macharius held that his true task was nothing less than "to reforge the spirit of the Imperium itself in fire, blood, and steel". His campaign was colossal in scope, "the largest single military effort the Imperium had undertaken since the Emperor’s Great Crusade". The Lord Solar chose the Segmentum Pacificus because he knew a wide swath of space within it had been lost to the Imperium millennia ago and never reclaimed, due to the upheavals during the dark days of the Age of Apostasy. His ambitions, though, stretched much farther, out to the limits of the galaxy and even beyond.
His forces mustered at the edge of the segmentum in seven great army groups before sweeping out across the stars into dozens, then hundreds, of individual campaigns. Macharius was everywhere at once, taking his forces in the mighty First Army Group wherever they were needed, for "he was never willingly far from the battlefield". He engaged in personal combat without hesitation, leading the final decisive assault of many campaigns. His unmatched zeal was legendary, the force of his presence on the field incalculable. "Many claimed that even mortally wounded soldiers would rise and fight on if the Lord Solar asked it of them".
"A hundred worlds are said to have fallen to the Lord Solar’s troops during the first year of the conquest, with hundreds more being taken each year thereafter". By late in the second year of the campaign, Macharius’s forces had taken the majority of the worlds that made up the sector which would one day bear his name. Most of these worlds had previously been part of the Maphian Sector, though this designation had been laid down during the Great Crusade and, as the Imperium’s control over the region crumbled, had not been heard outside the dusty vaults of the Administratum for millennia.
After a huge celebration, the conquest was expanded manyfold, by the rarest of events: the accession of multiple Adeptus Astartes Chapters to the campaign. The fiercely independent Space Marines do not ever take orders from other Imperial forces, and they seldom deign to even inform their allies when they intend to act. Nevertheless, the scope of Macharius's conquests had become so massive that those born for war "could not resist" participating. Multiple Space Marine Chapters, including the legendary First Founding Space Wolves of Fenris, began to coordinate their direct support with Macharius’s army groups.
What had begun as a massive military conquest took on a holy fervour, with many soldiers believing that "Macharius was clearly chosen by the Emperor himself for the task of reclaiming lost worlds — a belief the Lord Solar was thought to subtly encourage, for he may well have believed that it was so". Macharius regularly spoke of bringing the Emperor’s light to worlds long lost to darkness, and the great gift of delivering it to ones that had never known His grace before. The Ecclesiarchy certainly accepted this as true, and soon the conquests were regularly being called, even in official Imperial documents, the Macharian Crusade.