'Commander' in the Bible

Rehum the commander and Shimshai the scribe wrote a letter concerning Jerusalem to King Artaxerxes as follows:

From Rehum the commander, Shimshai the scribe, and the rest of their colleagues -- the judges, the rulers, the officials, the secretaries, the Erechites, the Babylonians, the people of Susa (that is, the Elamites),

The king sent the following response: "To Rehum the commander, Shimshai the scribe, and the rest of their colleagues who live in Samaria and other parts of Trans-Euphrates: Greetings!