Who was the First Commander in Chief of the Kaurava Army?

Bhishma (Bheeshma) was the first commander-in-chief of the Kaurava army, appointed by Duryodhana at the start of the Kurukshetra war. He led the Kaurava forces for the first 10 days of battle before falling to Arjuna. Drona succeeded him as commander after his injury, and Karna took command later. Ashvathama became commander only much later, after Drona's death.