Quintus Curtius Rufus, History of Alexander 8.11.11

8.11.11

sed ut signum tuba datum est, vir audaciae promptae conversus ad corporis custodes sequi se iubet primusque invadit in rupem. Nec deinde quisquam Macedonum substitit, relictisque stationibus sua sponte regem sequebantur.

And at first, because the peril was so palpable, a resolution was passed that the king should not hazard his safety by taking part in the assault. But when the trumpet sounded the signal, the audacious prince at once turned to his body-guards, and bidding them to follow was the first to assail the rock. None of the Macedonians then held back, but all spontaneously left their posts and followed the king. Many perished by a dismal fate, for they fell from the shelving crags and were engulfed in the river which flowed underneath — a piteous sight even for those who were not themselves in danger. But when reminded by the destruction of their comrades what they had to dread for themselves, their pity changed to fear, and they began to lament not for the dead but for themselves.