When did muslim armies invade syria and iraq?
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When did Muslims led by general Khalid ibn al-Walid invade what is now Iraq?
633
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When did Muslims later led by general Khalid ibn al-Walid invade what is now Syria?
May 634
Islamic State of Iraq and the Levant
https://en.wikipedia.org/wiki/Islamic%20State%20of%20Iraq%20and%20the%20Levant
Muslim conquest of the Levant
https://en.wikipedia.org/wiki/Muslim%20conquest%20of%20the%20Levant
Muslim conquest of Persia
https://en.wikipedia.org/wiki/Muslim%20conquest%20of%20Persia
Arab Muslims first attacked Sassanid territory in 633, when Khalid ibn al-Walid invaded Mesopotamia (then known as the Sassanid province of Asōristān; roughly corresponding to modern-day Iraq), which was the political and economic centre of the Sassanid state.[4]
Muslim conquest of Persia
 Arab Muslim forces had appeared on the southern borders even before the death of Muhammad in 632, resulting in the Battle of Mu'tah in 629, but the real conquest 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.[1]
Muslim conquest of the Levant
Khalid ibn al-Walid ibn al-Mughira al-Makhzumi (Arabic: خالد بن الوليد بن المغيرة المخزومي‎, romanized: Khālid ibn al-Walīd ibn al-Mughīra al-Makhzūmī; died 642) was an Arab Muslim commander in the service of the Islamic prophet Muhammad and the caliphs Abu Bakr (r. 632–634) and Umar (r. 634–644) who played a leading role in the Ridda wars against rebel tribes in Arabia in 632–633 and the early Muslim conquests of Sasanian Iraq in 633–634 and Byzantine Syria in 634–638.
Khalid ibn al-Walid
Muslim armies led by general Khalid ibn al-Walid first attacked Mesopotamia which is now known as modern-day Iraq in 633. Muslim forces later invaded Byzantine Syria in May 634.   