Mob

• It was originally intended by Horus that Ferrus Manus would join the rebellion and that the Iron Hands forces would arrive either during Isstvan III or shortly afterwards. When this proved not to be the case - due to Fulgrim being unable to sway him to Horus' side - Horus realised that he would have to factor the Iron Hands into his plans to deal with the inevitable Imperial counter-attack, and that this would cause additional, unplanned casualties amongst the Astartes loyal to him.
• Horus orders Fulgrim and the portion of the Emperor's Children not fighting on Isstvan III to proceed to Isstvan V and create a fortified position there.
• The Emperor orders 7 Legions - the Iron Hands, Salamanders, Raven Guard, Word Bearers, Night Lords, Iron Warriors and Alpha Legion - to assault Isstvan V. Unable to transport the entirety of his legion to Isstvan V on time - due to fleet damage inflicted by the Emperor's Children earlier - Ferrus elects to travel in the Ferrum (relatively undamaged) with his Morlocks (his Terminator elite).
• Fulgrim chooses a ruined fortress and defensive wall emplacement on Isstvan V as the building block for his fortification. With the aid of the Mechanicum he builds a vast network of trenches, bulwarks and redoubts, complete with anti-aircraft batteries and surface-to-orbit missile silos, in and around this ruin.
• Horus's forces move to Istvaan V from Istvaan III, including millions of Army soldiers, tanks and artillery pieces under Lord Commander Fayle and the Titans of Legio Mortis
• The forces of the Salamanders and Raven Guard arrive at Isstvan V first and achieve orbital superiority apparently uncontested. They undertake observation and reconaissance missions and are able to map out the traitor's position accurately and realise it requires a full-scale ground assault to destroy it. The Iron Hands contingent arrives next and the three Primarchs hesitate, both as their orders stipulate the 7 legions should attack together and because they realise that they cannot ensure victory without additional support. Upon learning that the 4 remaining legions are mere hours away from translating in-system, Ferrus convinces Corax and Vulkan to attack immediately; Corax to secure the right flank of the battlefield, Vulkan the left and Ferrus Manus will head up the centre.
• The World Eaters, Sons of Horus, Death Guard and Emperor's Children take up positions in line at the front of their defencework, with long range support units and Army artillery pieces kept to the rear, with Dies Irae ready to offer direct heavy support. The Traitors numbered 30,000 Astartes put together.
• The Loyalists launch a brief orbital barrage all along the length of the Traitor defensive position, but this proves almost totally ineffective due to the completeness of the defences. This is followed up by an immediate massed drop-assault directly in front of the Traitor position, with Ferrus Manus leading his Iron Hands immediately forwards into vicious defensive fire. In total, almost 40,000 loyalists hit the traitor lines. Dies Irae eliminates hundreds of loyalists with close support fire. Around 100 traitors - Death Guard and Sons of Horus sally out and engage Ferrus Manus and his Morlock advance unit, but are quickly defeated and retreat in the face of the Primarch's advance. At the same time, the Salamanders under Vulkan breach the line - the traitors respond with a pinpoint artillery strike on his position that slays dozens of his Firedrakes but barely affects the Salamanders Primarch. As the Iron Hands and Salamanders penetrate the traitor defences, the battle looks to be in the loyalists' favour.
• The support elements of the loyalists first wave land in their deployment zones, heavy landers beaching Astartes and Army armour units (including Super-Heavy tanks) as well as artillery. Many dropships are shot down by traitor AAA fire, and with casualites taken into account it's now reckoned about 60,000 Astartes are fighting.
• The traitor line bends like a bow, Ferrus Manus' assault pushing the furthest. The Raven Guard make their move, slicing into the traitor's flank with a massed jump-assault. This is met with a riposte led by Angron, whose World Eaters ambush and slay many loyalist Astartes. Mortarion's section of the line proves unbreakable, the Death Guard standing their ground. The Sons of Horus are spread all along the line, commanded by subordinate officers. Abaddon and Horus Aximand fight together, killing all who come near them.
• The Iron Hands meet the Emperor's Children and their advance stalls against the visibly depraved traitor marines and their unexpected use of sonic weaponry.
• Imperial armour units manage to advance far enough to support the Iron Hands, giving them some forward movement. Loyalist armour and artillery also focus their fire on the Dies Irae, stripping it's void shields and forcing it to cease firing on infantry and engage in tank-busting. Thousands are now dieing every minute.
• Julius Kaesoron meets and kills Gabriel Santar in single combat.
• The loyalist second wave (Word Bearers, Night Lords, Iron Warriors and Alpha Legion) arrive, executing successful combat drops in the Imperial landing zone, and begin both fortifying it and securing the Imperial flanks. The sight of this force - more than doubling the loyalist forces at a stroke - appears to force a general fighting retreat on the part of the traitors, with even Angron, Mortarion and the Dies Irae leaving the field.
• Ferrus Manus locates Fulgrim's position and orders his Morlocks to assault it. Corax urges his brother to fall back to the landing zone to resupply and return with fresh support from the other legions - as he intends to do - but Ferrus Manus refuses. Both Corax and Vulkan order their battered legions back to the landing zone, leaving Ferrus and the Iron Hands unsupported.
• The Morlocks assault Fulgrim's redoubt, engaging in battle with his signifcantly outnumbered Phoenix Guard. Ferrus Manus confronts Fulgrim and the two choose to initially duel with words instead of weapons.
• The Raven Guard and Salamanders, low on ammunition and heavy on casualties, get to within 100 metres of the landing zone fortifications when vox-contact with the second wave forces is cut. A single flare is launched from Horus' command post...signalling the second wave - revealed as traitors - to open fire. Their first salvo decimates the unsuspecting Raven Guard and Salamanders legions.
• Corax and Vulkan disagree upon which course of action to take; Vulkan advocates securing the first wave dropships and digging it, Corax - realising the battle is already lost - prefers to immediately evacuate and orders his legion to retreat by any means necessary.
• Both Corax and Vulkan appear to take direct artillery strikes on their positions - Corax is seen surviving his, but Vulkan disappears in the midst of sizable mushroom cloud.
• The supposedly retreated traitor legions turn around and hurl themselves at the Iron Hands units, seemingly slaughtering them to a marine.
• Fulgrim and Ferrus Manus duel to the death. Eventually, Fulgrim emerges the victor, beheading his defeated brother.
• Fulgrim gives in to daemonic possession.
• With the annihilation of the Iron Hands, the Raven Guard and Salamander forces are caught in a vice of traitors and massively outnumbered. They continue to fight rather than attempt to flee for some time, but only succeed in ensuring their systematic destruction. The Dies Irae returns to the field, as do Mortarion and Angron, and all three cause tens and tens of deaths. Fulgrim - now secretly possessed by a daemon - quits the field completely, leaving the Emperor's Children to be led by Eidolon and Lucius.
• Horus himself enters the battle, leading Falkus Kibre and the Justaerin Terminator elite, with Abaddon and Aximand fighting their way to him, and then alongside him.
• Small, scattered elements of both the Raven Guard and the Salamanders manage to break out of the battlefield - now a massacre site - and make it to undamaged drop-ships, managing to flee the area. More Raven Guard than Salamanders escape, the Salamanders suffering heavily at the hands of the Night Lords and Alpha Legion. Perhaps miraculously, considering the odds, a few Iron Hands marines manage to link up with an escaping Salamanders unit and survive.
• Corax - although wounded - escapes. Of Vulkan there is no sign.

• Corax's thunderhawk is shot down on the other side of the hills that form the urgall plateau, causing further casualties. The primarch regroups the survivors. Estimated RG casualties are between 75 and 90%.
• Corax assembles as many RG still on the planet that can be contacted upon a highland hill. (4,000 - potential error;see notes) An roaving Iron Warriors armour column threatens to uncover them, so he orders it ambushed and destroyed. Setting up a base of fire with his surviving tactical units, he has his assault units distract the IW outriders and fall on them from one flank. He individually attacks the other, having disperesed his bodyguard unit into the other squads. The Iron Warriors coumn is wiped out and scavenged for supplies, before the RG move out to seek a new hiding place.
• 30 days afyer the drop, the RG survivors have heard no word from the Salamanders or Iron Hands. Corax orders his troops to assemble on the lurgan ridge, then goes on a lone reconaissance of the urgall plateau, using the mt tor vendis as an eyrie to spy on the drop zone, still awash with traitors. He uses his secret 'invisibilty' (psi-clouding) power to prowl the enemy camp. He is unable to find the bodies of Vulkan or Ferrus Manus.
• The RG are pinned down on the ghula plain, hunted by the World Eaters legion led by Angron.3K \rg vs all of the WE
• 98 days in. The WE bombard the RG with whirlwinds, but before they can advance they come under concentrated orbital bombardment and air to surface missile strikes from RG dropships which suddenly appear. These dropships, under the command of Imperial Army Prifector Valerious and part of a mission led by RG Commander Bran, quickly evacuate the RG in the brief window they've fought for themselves. 80K RG arrived at IV, less than 3K leave.