Why should he depict a siege around the city?
Malbim: This shows that via its sin, Hashem put enemies around it to besiege it to destroy it. Hashem, who builds it, engages in destroying it.
What is "Dayek"?
Rashi: It is a catapult used to cast rocks against a city.
Radak: It is a wooden tower built against a city to conquer it.
Malbim (21:27): It is a wall around the city wall, to stop people from leaving the city.
What is "Solelah"?
Rashi: He spills earth and compresses it with sticks and makes a tall mound to stand on it, see into the city and shoot arrows.
Radak: They spill earth in trenches around the city to fill them, and make a tall mound to ascend from it to the wall, or to fight against it.
What are "Karim"?
Rashi citing Targum Yonasan: They are troops stationed around a city in all directions. They dwell in tents, and prevent people from coming and going. Karim are the officers appointed over the army; they guard in different directions.
Radak: They are army officers.
Radak citing his father: They are sheep. This is like "Im Cherev Karim" (Devarim 32:14). They make iron rams to gore (batter) the wall.