द्रोणं च भीष्मं च जयद्रथं च कर्णं तथाऽन्यानपि योधवीरान्। मया हतांस्त्वं जहि मा व्यथिष्ठा युध्यस्व जेतासि रणे सपत्नान् ॥

droṇaṁ cha bhīṣhmaṁ cha jayadrathaṁ cha karṇaṁ tathānyān api yodha-vīrān mayā hatāṁs tvaṁ jahi mā vyathiṣhṭhā yudhyasva jetāsi raṇe sapatnān

Drona and Bhîshma and Jayadratha, Karna, and all the other warriors here, Are slain by Me. Destroy them fearlessly. Fight! thou shalt crush thy rivals in the field.

In plain words: Krishna names the great warriors on the other side, like Drona, Bhishma and Karna, and says he has already killed them. He tells Arjuna to fight without fear because he will win.