Complex sentence: When Selim started his march east, the Safavids were invaded in the east by the Uzbek state recently brought to prominence by Abu'I-Fath Muhammad, who had fallen in battle against Isma'il only a few years before.
Split into simpler sentences: When Selim started his march east, the Safavids were invaded in the east by the Uzbeks. The Uzbek state had been recently brought to prominence by Abu'I-Fath Muhammad, who had fallen in battle against Isma'il only a few years before.