 Complete the following phrase:  Neither empire was given any chance to recover, as within a few years they were struck by the onslaught of the Arabs newly united by Islam, which, according to Howard-Johnston, can only be likened to a human tsunami. According to George Liska, the unnecessarily prolonged ByzantinePersian conflict opened the way for Islam. The Sasanian Empire rapidly succumbed to these attacks and was completely conquered. During the ByzantineArab wars, the exhausted Roman Empires recently regained eastern and southern provinces of Syria, 