Keil & Delitzsch

"At that time," i.e., when Jehoiachin had come to the throne, or, according to Ch2 36:10, "at the turn of the year," i.e., in the spring (see at Kg1 20:22), the servants (generals) of Nebuchadnezzar marched against Jerusalem, and the city was besieged. The Keri עלוּ is substantially correct, but is an unnecessary alteration of the Chethb עלה, since the verb when it precedes the subject is not unfrequently used in the singular, though before a plural subject (cf. Ewald, 316, a.). The נב עבדי are different from the גדוּדים of Kg2 24:2. As the troops sent against Jehoiakim had not been able to conquer Judah, especially Jerusalem, Nebuchadnezzar sent his generals with an army against Jerusalem, to besiege the city and take it.