Valmiki Ramayana Yuddha Kanda Sarga 109 Shloka 1

ततः thereupon, तदा then, रामरावणयोः for Rama and Ravana, सुक्रूरम् fierce, सुमहत् great, सर्वलोकभयावहम् fearsome to the whole world, धैरथम् duel, युद्धम् war, प्रवृत्तम् ensued

Then there ensued a fierce duel between Rama and Ravana that was fearsome to the whole world. Rama and Ravana continue to fight raining arrows at each other. Rama breaks the flag post of Ravana's chariot.