'Commander' in the Bible

Rehum the commander and Shimshai the scribe wrote a letter against Jerusalem to King Artaxerxes, as follows—

then wrote Rehum the commander and Shimshai the scribe and the rest of their colleagues, the judges and the lesser governors, the officials, the secretaries, the men of Erech, the Babylonians, the men of Susa, that is, the Elamites,

Then the king sent an answer to Rehum the commander, to Shimshai the scribe, and to the rest of their colleagues who live in Samaria and in the rest of the provinces beyond the River: “Peace. And now