1)
What is the meaning of "Shosim"?
1.
Radak: They are despoiling. This is like "Zeh Chelek Shoseinu" (Yeshayah 17:14).
2.
Malbim (citing Eruvin 45a): The Plishtim came on Shabbos, merely for straw -- "v'Hemah Shosim Es ha'Garanos." Even so, since the city was near the border [of Eretz Yisrael], Chilul Shabbos was permitted 1 [to fight them, lest it lead to their conquest of Eretz Yisrael]. Shosim implies intent to destroy, as opposed to Bozez (taking for one's benefit).
1
Malbim: Chazal inferred so, for Lochem Al Ir is trying to breach the wall. Lochem b'Ir (like it says here, bi'K'ilah) is when they enter the city and fight with its residents.
