A: Baghdad, Al Saadoon Park, Baghdad Governorate, Iraq
The first recorded exposition of any kind of cryptanalysis was the discussion of frequency analysis by the Muslim Arab philosopher, mathematician, physician and musician Abu Yusuf Yaʻqūb ibn Isḥāq al-Sabbah al-Kindī (Arabic: ابو يوسف يعقوب بن اسحاق الصبّاح الكندي) in his treatise on Deciphering Cryptographic Messages written in Baghdad about 850 CE.
It was suggested that close textual study of the Qur'an showed that Arabic has a characteristic letter frequency, to which frequency analysis could be applied.