The Battle of al-Qādisiyyah (Arabic: معركة القادسيّة‎; transliteration, Ma'rakatu al-Qādisiyyah; Persian: نبرد قادسيه‎; alternative spellings: Qadisiyya, Qadisiyyah, Kadisiya), fought in 636, was the decisive engagement between the Arab Muslim army and the Sassanid Persian army during the first period of Muslim expansion. It resulted in the Islamic conquest of Persia and was key to the conquest of Iraq.