Imperium fatally overstretched?

In 03.029M42 it appeared the imperium had reached their zenith in the sector. Since the coming of the Cicatrix the forces of mankind had established bases in the Foramen, allowing them to conduct sweeping campaigns in the newly accessible Hadron Expanse. The imperium has conquered Awarath, Dnatha, Hussaria and Palantir, and held on to their gains despite concerted attacks from chaos and the alliance. The imperial fleets had reached as far as Hexis, and established an army there, even controlling the vital necron device for a while. 

However, by the end of 03.019M42 cracks on the imperial strategic position had become yawning chasms. The defences in the Foramen systems of Paradorn and Destino had not been strong enough for a combined assault by the forces of chaos and the perfidious eldar, who arranged a temporary alliance in order to harm the imperial cause. The Zadoc subsector had been bypassed, leaving dangerously powerful alliance and chaos worlds in the imperial supply rear. Worst of all, the former Crusade Mechanicum Archmagos, Cybixx, had been left to his own devices at the critical system of Vandrax. 

Following the collapse of the crusade and inquisitor Vorushko’s order to stand down for the good of mankind, Cybixx had rebelled. However Vorushko was now far off in the Expanse, tending to the new worlds and overseeing events on Hexis. Cybixx, she left to Inquisitor Hathek. 

This was a tragically unwise move. Hathek had no resources with which to monitor the renegade Magos. First, Cybixx rebelled against the imperium. Finally, in 019M42 he revealed the full extent of his heresy. Declaring for chaos on 2003.019M42, the systems of Vandrax and most of Destino now fell to the ruinous powers. At the same time, the Emerald Serpent wiped the imperium off the map in the Foramen Interdictum. 

Even the eldar were alarmed by this turn of events, and now that Maximus’ forces in the Imperium Nihilis were cut off, the eldar ended their agreement with chaos. The war in the Foramen would continue - between chaos and the Aeldari. 

In the dark imperium resources dried up. Unable to adequately supply their armies, Maximus ordered a scorched earth policy as his forces went over to the defensive sector wide. The alliance and chaos armies must pay in blood for every inch of the emperor’s lands he ordered, and training in guerrilla and rearguard actions was stepped up across the region. The imperium would be unable to take ground off their enemies, but if they could grind down chaos and alliance forces in protracted wars of attrition, they might be able to hold on long enough to launch a new campaign against the Foramen that were a lifeline to their armies.