Assalamu Alaikum, question about the miraculous sign in Surah Ar-Rum

Hey everyone, I was hoping to put together a video discussing one of the amazing signs in the Quran, specifically the verses in Surah Ar-Rum about the Romans eventually gaining victory. It talks about their defeat and then their triumph. My main question is: how can we be sure that these verses were actually revealed while that war was still going on? I'd love to hear your thoughts on this.