Duryodhana now issues a direct command to his commanders: "Hold your assigned positions at every front, and above all, protect Bhishma from every side."
He knows that Bhishma is the spine of the Kaurava army. As long as Bhishma stands, the Kaurava formation holds. Losing him early would be devastating. So Duryodhana makes his priority clear: Bhishma's safety comes first. From a military standpoint, this is sound strategy: guard your strongest asset.
Yet there is an irony here that the Mahabharata does not miss. Bhishma was so powerful that he needed no one's protection. Duryodhana's urgent command reflects his own insecurity more than any real danger to the grandsire. He fears the Pandavas might find a way to bring Bhishma down. And eventually, they did.