Daniel 9:1 Midrash

בִּשְׁנַ֣ת אַחַ֗ת לְדָרְיָ֛וֶשׁ בֶּן־אֲחַשְׁוֵר֖וֹשׁ מִזֶּ֣רַע מָדָ֑י אֲשֶׁ֣ר הָמְלַ֔ךְ עַ֖ל מַלְכ֥וּת כַּשְׂדִּֽים׃

In the first year of Darius the son of Ahasuerus, of the seed of the Medes, who was made king over the realm of the Chaldeans;

Read midrashic interpretation of Daniel 9:1: and classical rabbinic exegesis.