Burning of Anahktor
The war was waged on Anahktor, a planet no longer listed in any Imperial records save the Great Library of Terra but a close distance via the warp to Anvillus. The planet at the time of the Great Crusade was a small haven of humanity that had weathered the worst of the Age of Strife thanks to decisive leadership and a small but effective defense fleet. It primarily survived on plundering and enslaving nearby systems. After attacking scout vessels belonging to the Imperium, a host of 12 Companies of Blood Angels was dispatched under Sanguinius himself. In a short but brutal engagement, Sanguinius' vessels broke the enemy fleet and pushed to the first inhabited planet of the Anahktor system, the small airless orb of Anahktor Extremis whose population existed underground.
Sanguinius immediately assaulted the small world with elements of the 19th, 67th, 171st, and 94th Companies after a brief orbital bombardment. The Blood Angels swiftly reached the cold subterranean halls of Anahktor Extremis where they confronted enemy soldiers that barely resembled humans. Dubbed "Iron Bulls" by the Blood Angels, they wielded primitive plasma casters and grav-lances. They held back the Blood Angels for six hours with tenacious courage before being overwhelmed and annihilated. All across the outer worlds of Anahktor, the same story played out. The enemy was beset by the Blood Angels and fought courageously to the bitter end. In asteroid fields around the outer system, the Iron Bulls staged ambushes and feigned retreats to draw the Blood Angels in further. On Anahktor Median they drew a line with their own bodies, fighting a sprawling battle across 80 kilometers of shallow acidic seas atop multi-legged augmetic frames. The Blood Angels came to admire their foes, and took great pride in their victories against them. Sanguinius himself gave the order for a six hour ceasefire in honor of their foes valor and sacrifice. Privately, the Primarch lamented the destruction of these foes and hoped that the pause could allow for a peace of some sort to arise.
The Anahktorians responded by sending vessels under the flag of truce towards the Red Tear baring gifts for the Primarch. However the Anahktorians revealed their true intentions when the vessels exploded by the Blood Angels flagship, killing 132 Legionaries and damaging three Cruisers, one of which (the Inculcator had to be completely abandoned from the devastation wrecked. Betrayed, Sanguinius slipped off the collar of discipline and unleashed a savage reckoning on Anahktor. The Blood Angels launched a barrage of nuclear weapons upon every enemy stronghold they could find. In desperation, the Anahktorians attempted to use civilians as human shields but this proved to no avail. Blood Angels ships enveloped Anahktor Centralis and unleashed the Angel's Tears onto the surface via Drop Pod as the Iron Bulls attempted to use civilians to shield their defensive positions. What followed next was a slaughter as the Angel's Tears destroyed the Iron Bulls leadership. Forbidden Phosphex and Rad Weapons were unleashed. Any who opposed them were slaughtered, human shield or not. The last of the Iron Bulls was cut down by Sanguinius himself before capturing the King of the Anahktorians. Sanguinius dragged the lordling outside to witness what had befallen his world before executing him. Anahktor Centralis was not conquered, but instead devastated.