Taros Campaign - Breakthrough on the Iracunda Isthmus: Since the offensive towards Tarokeen had stalled there had been little fighting between the Tallarn regiments and the Tau. The Tallarns had made small, local advances and continued harassing artillery fire but, short on supplies and critically short on water they had started to dig in to conserve what supplies they had left. Whilst the Imperial Guard were not advancing the Tau did not counter-attack. With the Imperial Guard marooned in the desert, the Hunter Cadres conserved their own strength for the battles still to come.It was critical to the success of Operation Comet, and maybe the outcome of the whole war, that a relief force reached the Drop Troops at Hydro-Processing Plant 23-30 in three days. Before any relief force could make its advance, a breakthrough had to be made through the western end of the lracunda Isthmus. The ground forces would have to break into the lracunda Isthmus, using the narrow strips of land between the small seas and Jakes in the area. Channelled by the terrain, any attack would have to be directly into the teeth of the waiting Hunter Cadres' firepower. The Tallarn regiments were no longer fit for the offensive. They had lost many men and most of their tanks in the long drive north. The war was entering a critical phase; much rested on Operation Comet succeeding. De Stael turned to the best troops he still had. Firstly, the Raptors Space Marines. Captain Orelius' battle brothers had seen little ground action; it was time to commit them again. The Space Marines would be the spearhead of the thrust, supported by the Titans of Legio Ignatum. The Warhounds were the Imperium's largest war machines on Taros, and it was unlikely the Tau had any answer to them. Between these two forces, they would smash through the narrow terrain, sweeping aside any resistance and clearing the way for the mechanized 114th Cadian regiment to strike north and reach the hydro-plant. The breakthrough operation would begin on the same day as the Elysians launched Operation Comet.Captains Orelius and Kaedes oversaw the Space Marines' preparations for the attack, and the battle brothers of 2nd and 6th companies mustered for an armoured engagement. Thunderhawk Transporters plunged from orbit to land at the assigned assembly area, just west of the northern end of the Isthmus entrance. On board the transporters were Land Raiders, Predators, Whirlwinds and Rhinos, all carrying the squads of 3rd company. The attack would come swiftly, giving the Tau minimal time to respond, and it would come in overwhelming force. It would be spearheaded by the armour of the Raptors Chapter supported by the firepower of the Warhound Titans, with the 114th Regiment awaiting the breakthrough to begin their own mission - the relief of Hydro-Processing Plant 23-30. While the Space Marines assembled, the Warhound Titans of Legio Ignatum were stalking north to join them, striding through the deserts accompanied by the sprawling Chimera formations of the Cadian regiment. For the first time in the campaign, the Tau would experience a true army of the Imperium, the combined weight of the Imperium's fighting forces committed as one. Eight hundred kilometres to the south, the Valkyries and Vultures of the Elysian Drop Troop Regiment were just taking off as the Space Marines and Warhounds went into battle. Their target area was at the northern end of the entrance to the Isthmus. Their objective was to clear all Tau forces, punching a gap for the Imperial Guard to race through.The Tau's Pathfinder forward observers must have seen the Warhound Titans, standing fourteen metres tall above the desert, as they stalked forwards. The Tau were prepared for an attack and, as ever, their Hunter Cadres responded quickly to the call from their forward scouts. In earlier engagements, the Tau had always been able to make the most of their long-ranged weaponry to pick off Leman Russ Tanks and Chimeras. Now they faced Titans, equipped with huge weaponry and protective Void Shields; the advantage lay with the Imperium. This would be a different battle. The Warhounds engaged the Hammerheads at maximum range, blazing away with massive Turbo-Laser Destructors. The Space Marines sped forwards, Land Raiders leading the way, Whirlwinds in close support, Predators on the flanks. Hoping to halt the assault, the Tau could no longer simply give ground before the attack, they had to stand and fight. This was to the Space Marines' advantage. The Raptors strike force could close the distance and start to engage with their highly accurate Lascannons. Conducted with speed, accuracy and their trademark aggression, the Space Marines tore into the Tau defenders, deploying Devastator squads from Rhinos to lend their fire support. Suddenly the Tau were suffering heavy losses. With Void Shields flaring against Railgun hits, the Warhounds strode forwards, obliterating entire vehicles with a single hit from their weaponry, and stomping on the wreckage as they advanced. For the first time on Taros the Tau fell back having had the worst of an engagement. The desert was marked by tell-tale columns of smoke rising from the burning hulks of Tau vehicles.The Warhounds continually stalked forwards, obliterating anything in their path. Along with the Space Marines now advancing about their feet, the combined force thrust a sword clean through the Tau defences and opened the way onto the lracunda Isthmus. The Tau rallied, and the arrival of fresh Hunter Cadres saw the fighting intensify again. This time the Tau would deploy a new weapon. No Imperial commander had ever encountered this new mark of Tiger Shark before. The aircraft came in fast, skimming the desert so low it kicked up a dust cloud, before climbing over a shallow rise to open fire. Missiles rippled from the aircraft's wings, flaring bright against Warhound Advensis Primaris’ Void Shields. The explosions overpowered the generators, which cut out. The following shots from the Tiger Shark AX-1-0’s twin Heavy Railguns struck the Warhound squarely in the hull. With devastating power two hyper-sonic shots tore through the thick armour plate in an explosion that showered the surrounding desert in molten shrapnel. Critically wounded, the Warhound staggered backwards under the impacts, tottered and, to the astonishment of all, fell.Where once Imperial Commanders had thought the Titans untouchable to all but a Manta's firepower, suddenly the Tau had a new tactical weapon capable of killing the mighty war machines . The wreckage of Advensis Primaris lay billowing oily smoke as the sand settled over her. Inside the crew lay dead at the controls, including High Princeps Jernay, killedby the agonised screams of pain that led directly into his brain from the Titan's mind-impulse controls. It was a bitter and unexpected loss. The remaining three Titans withdrew rather than face another strafing run. Their mission was already complete; the 114th Cadians were now able to begin their strike northwards, and further Titan losses would be for no further gains.The Space Marines and Warhounds had advanced the required fifty kilometres in just a day of fighting. Skirmishing continued in the area all day, with Space Marine patrols hunting down any alien stragglers or Pathfinder teams bold enough to return to the battlefield. Behind them the 114th Cadians roared their engines into life. Despite the victory, the loss of Advensis Primaris was a worrying development. The Tau had learned from their previous experiences fighting the Imperium's greatest war machines. In the past, Hunter Cadres had been roughly handled by Titans, but now the Tau had developed a weapon capable of fighting back. The new Tiger Shark had been upgraded to carry two Heavy Railguns, sacrificing its standard payload and Ion Cannons for the kind of firepower usually only mounted on Mantas or spacecraft.