And now.
The High Lords all knew about this.
That meant every High Lord was surely making preparations on two fronts.
On one hand, they believed nothing would happen. On the other, they prepared to quietly hand over the secrets of the other High Lords to demonstrate their own loyalty. After all, to these High Lords, suppressing the power of others and preserving their own mattered more. Of course, they also understood that if they appeared too weak, the arriving Chapters would inevitably deal a severe blow to their interests.
Those Astartes still could not be allowed into Terra. Even if the High Lords' authority was severely restricted, they had to uphold an absolute bottom line: restrain the Astartes and ensure that all power in the Imperium remained in the hands of true humans. That was the inviolable line.
The Astartes could have military rank in wartime.
But they absolutely could not be granted political power. They would forever remain tools of the Imperium.
The High Lords had already begun to reveal their weakness.
But that did not mean the people represented by the High Lords were willing to surrender outright. The High Lords were merely the representatives of their power. The ones who truly reaped the greatest benefits were often the families behind those High Lords: Navigator Houses, Knight Houses, nobles enfeoffed by the Imperium, and so on.
Getting these people to act, much less to temporarily set aside their own interests for those of the Imperium, had never been realistic. The Imperium could be destroyed, humanity could be destroyed, but their own power, their family influence, their vast aristocratic empires absolutely could not be eradicated.
Even if the High Lords gave up protecting their power, they would take the initiative to band together and resist the Imperium's orders.