1:1 twentieth year. That is, the twentieth year of Artaxerxes’ reign (Nehemiah 2:1). This would be thirteen years after this same king sent Ezra to Jerusalem (Ezra 7:7).
1:1 Shushan. Shushan is the same as Susa, the winter capital of the great Persian empire, about 250 miles east of Babylon, well identified and confirmed archaeologically.