Valmiki Ramayana Yuddha Kanda Sarga 94 Shloka 20

ते those, रजनीचराः night rangers, रणे in war, रामेण by Rama, कृतानि deeds, सुघोराणि terrible, असुकराणि difficult for others, रामस्य Rama's, कर्माण्येव his action, ददृशुः could not see

The night rangers were able to see Rama's terrible action which was difficult for others only after he had performed not otherwise (as they could not see his quick movement).