Death Guard - Pre-Heresy: Before they were reunited with their Primarch, the Dusk Raiders conformed very closely to the standard raiment of arms and organisational patterns laid out for the early Space Marine Legions by the Imperial Officio Militaris. At its most fundamental level the Dusk Raiders Legion was organised around the principle of equipping its individual Space Marines as well as possible, so that they could endure and prevail against any foe encountered and operate for extended periods without resupply or support if necessary.This dogma was the cornerstone of the XIVth Legion's way of war, and was built upon the foundations of independence and surety with which the Dusk Raiders had always fought. The Dusk Raiders are noted in the Imperial records of this period as maintaining a well-rounded capacity for unleashing multiple modes of warfare, although with some bias towards heavy assault formations and attritional engagements, as evidenced by the particular use of close-ranged weaponry within the Legion.The Dusk Raiders Legion relied upon its infantry to provide its strategic strength, with the bulk of tactical fire support coming from heavily armed support squads, and later with considerable numbers of Terminators and Dreadnoughts providing reinforcement and an assault spearhead where needed.Once Mortarion became the master of the XIVth Legion the Death Guard changed dramatically, including its arts of warfare. Mortarion was at his heart an infantryman, and in his Death Guard he saw the chance to perfect the principle of the utilitarian warrior on foot who could go anywhere, fight on any ground and destroy any enemy through resilience, resolve and implacable aggression.As part of this doctrine, the Death Guard's squad formations were largely not static as in most Space Marine Legions of the time, but were formed, reformed and ordered as needed and as the given tactical situation required. To this end, a Death Guard Legionary was trained to be equally adept at any infantry role he might be called upon to perform on the battlefield rather than fighting at all times in a particular specialised role.In this way, a Death Guard Astartes would act as a Tactical Marine in one battle, a heavy weapons fire support specialist in another and so on, with only Techmarines and other highly specialised occupations remaining wholly dedicated to a single tactical role.The Death Guard was organised around the principles established by the Dusk Raiders and built upon the ways they had always fought. Bolter, Melta and Flamer became the Death Guard's trinity of weapons around which their wargear was based, keeping supply needs to a minimum. Other types of ranged weapons were deployed sparingly only as the tactical situation or nature of the enemy demanded.Each Death Guard also carried a close combat blade as well, which included broad trench daggers, Warscythes and the heavy slashing Kukra native to Barbarus. Forged of dense black ceramsteel, these brutal and efficient weapons soon became the hallmark of the Astartes of the XIVth Legion.This reliance on simple but effective tools of war was an outward manifestation of the cardinal belief held by the Legion that the Space Marine himself was the greatest of all weapons at the Imperium's disposal, a tireless engine of war before which any enemy would eventually succumb.The Death Guard continued to rely throughout the Great Crusade almost exclusively on its infantry to provide its strategic strength, with the bulk of tactical support firepower coming from heavily armed support squads, and later from the Legion's considerable numbers of Terminators and Dreadnoughts, which provided reinforcement and assault spearheads where needed.This focus on heavy infantry formations was also one of the reasons the Death Guard Legion developed a particularly admirable record in fighting to clear Space Hulks of alien infestation and for their ability to destroy fortifications and citadels from within.While the Death Guard did utilise field armour, support vehicles and transports (as Mortarion would not allow his forces to be circumvented, cut-off or left wanting for their lack), these were not given any primacy in the Legion's tactical doctrine. The only exception to this were dedicated siege units such as the Vindicator which was fielded in disproportionately high numbers by the Legion, alongside squadrons of Fellblade super-heavy tanks and Land Raider Spartans in mass warfare.It was notable in hindsight, and would prove to be a telling factor on Istvaan III, that a proportionately high number of the Death Guard Legion's war machine crews were still of Terran blood by the time of the Horus Heresy, while the heaviest infantry strike units, particularly the Legion's sizable core of Terminator Armour-equipped shock troops, were of Barbarus stock.Unlike some of the Space Marine Legions whose operations were often diffused across separate commands, taskforces and campaigns spread across the galaxy during the Great Crusade, the Death Guard were accustomed to fight as a single, united force. As such, when the XIVth Legion came to the Istvaan System at the start of the Heresy with almost its entire strength, the most accurate accounts of the time claim that the Death Guard maintained approximately 95,000 Space Marines, 70 capital ships and perhaps three times that number of smaller Escort and assault craft.With the conclusion of the bitter fighting on Istvaan III, it is estimated Mortarion's Legion had been reduced by well over 25,000 casualties, counting both the stubborn Terran Loyalists, betrayed to their deaths in the ash-mantled ruins of Istvaan III, and Mortarion's sons of Barbarus whose lives had been spent to purchase their demise.It is believed that protracted fighting during the Istvaan III Atrocity had exacted a heavy toll on the Death Guard's armoured divisions, many of which had been amongst the suspected Loyalists within the Legion. Though it is believed many vehicles had been recovered from the planet, very little time had been available to render them fully battle-worthy again.However, the fighting that was to occur during the Drop Site Massacre engagement was to suit the Death Guard Legion well, with its strong emphasis and preference on attritional warfare and close order infantry tactics.Evidence suggests that a large core of Death Guard Legionaries deployed to one flank of the Urgall fortress-line, into a network of trenches, bunkers and slip-tunnels swiftly, but expertly, prepared or augmented by the Legion. This provided them both with deep protection from bombardment and hid their numbers.