Rashi: When Melech Ashur will camp against Yerushalayim, I will camp against it, for he does so based on My command and desire. This is why it says "v'Tzarti" and "va'Hakimosi".

Malbim: I will camp around you with My soldiers.

Rashi: It is a line of troops surrounding [Yerushalayim]. Radak - it means around, like 'ha'Kador veha'Eimum' (Kelim 23:1). It is called so because it is round. The prefix Kaf or Beis is omitted. I will camp around you like a ball. This is like "Kadur El Eretz Rachavas Yadayim" (22:18).

Radak: I will besiege. This is like "Ki Satzur El Ir" (Devarim 20:19).

Targum Yonasan: I will build Karkom (a siege-wall) against it. Radak - this is like Targum Onkelos of "u'Vanisa Matzur" (Devarim 20:20).

Rashi: It is a siege-wall placed against cities.

Radak: It is a wooden tower that they erect against a city in order to capture it.

Rashi: Besieged. Radak - this is like "u'Vanisa Matzur" (Devarim 20:20). Even though it does not say in that Parashah that Melech Ashur built a siege-wall, it says "Lo Yavo El ha'Ir ha'Zos v'Lo Yoreh Sham Chetz v'Lo Yekademenah Magen v'Lo Yishpoch Aleha Solelah" (37:36). We infer that he prepared that day to spill on the next day, and made a wooden tower and a siege-wall. The angel struck them that night and annulled their plan.