Originally Posted by Lord Commander Solus
I suppose Horus did fight to get those things in the first place.
Horus was Warmaster, commander-in-chief of the Imperium's military. He had the initiative, the element of surprise and the time to initiate his plans. He had gathered support to the extent that a full-third of the Imperium's armies declared for him. He had as good as destroyed three Legions on the sands of Isstvan V and scattered several others to the wind. He was as good as given the advantages he possessed.
In The Crimson Fist
, Dorn and Sigismund discuss the probability of the war reaching Terra:
Originally Posted by The Crimson Fist
Sigismund echoed Dorn's frown. 'Horus has the initiative, we are the ones mired in confusion. He could cut us apart piece by piece, wait until we are so weak that there is no resistance left.'
Dorn looked sharply at Sigismund, but he could tell that his father had considered the same possibility.
'If it was Curze or Alpharius then perhaps, but they are not at the heart of this.'
'He will come here,' said Dorn softly. 'He will not stay out amongst the stars and bleed us to nothing. No, he is still Horus. The single spear thrust to the throat, the final killing blow. He will come here to finish this. One night we shall look up and see the heavens burning.'
Perhaps if he remained out amongst the stars he could have, as Sigismund suggested, triumphed by bleeding the loyalists dry. But he always intended to strike at Terra and his father, I can't imagine the alternative was ever an option in his mind.
Agreed and he did pull a full moron move by lowering his flagships void shields and inviting the most poweful Psyker, Dorn and Sanguinous to just head over there for a brawl. He was a genius tactician, yet in the end his obsession with showing his superiority and the need to challenge his father like that...kinda threw his chances out the window.
We don't know the exact reason why his shields were lowered.