First, Inquisition forces landed on the planet and launched their own assault on the Orks, without consulting with the Imperial commander, following their own agenda. The assault became a massacres, with the Orks taking the opportunity to move several miles closer to the planet's main spaceport after driving off what remained of the Inquisition forces.
This action undoubtedly stirred up the Orks, and greenskin reinforcements poured onto the planet days later, dropping from their crudely constructed "Roks", evading the small Imperial fleet in the system.
The Dark Angels reacted to this growing threat by throwing their weight against the Orks on Danelloth for the second time. The reinforcments were not of Nazghat's waagh, and Imperial speculation suggested the heightened violence on the planet had simply attracted more Orks in the vicinity to join the latest action. Lethbridge-Stewart contacted his superiors, warning that if the pattern continued, they would have awoken a hornets nest, and a new Waagh would fall upon the Zadoc subsector.
The Librian commander's concerns were taken as alarmist, and the Dark Angels pursued with their attack. In a bloody encounter the Orks managed to gain the upper hand, though fortune played a major part. Even so the 4th company were obliged to withdraw and several thousand Orks (some estimated as many a a hundred thousand) clustered around the Imperial perimeter, tightening the noose on Danelloth spaceport.