All the time I am seeing people complaining "Why does Grievous run away?" or "Grievous is a pansy". Well, I think I have an explanation for why Grievous was such a coward in RotS... It all starts with Star Wars: Clone Wars (2D). Grievous is briefly shown at the end of volume I, and plays a crucial role in volume II. Grievous in Clone Wars is a killing machine. He never runs and hides. He is not afraid of fighting four Jedi even. But then, at the end of volume II, when Grievous is boarding his ship with the captive Chancellor, Mace drops in to save the day. Grievous is ready to fight Windu, and Mace uses the Force and crushes Grievous' chest plates, which causes his coughing. Now, that is the reason why Grievous runs away in RotS and the new The Clone Wars show. He now knows he can be defeated and does not want to let that happen again. Anyways, that is my little "theory". If you have a theory, then please post it. I would like to see what other fans think on this matter.