Question: when did muslim armies invade syria and iraq
Answer: Arab Muslim forces had appeared on the southern borders even before the death of prophet Muhammad in 632 , resulting in the Battle of Mu'tah in 629 , but the real invasion began in 634 under his successors , the Rashidun Caliphs Abu Bakr and Umar ibn Khattab , with Khalid ibn al - Walid as their most important military leader .