Targum Onkelos and Targum Yonasan: It means 'When you besiege a town".

Rashi (in Bereishis, 2:i19): It means 'When you suppress a town'.

Rashi: It implies three days - "Yamim" implies two, ¹ and "Rabim" comes to add one more.

Rashbam: It implies a long time, with the result that one needs to cut down trees in order to build a fortification and ramps.

Targum Yonasan: It implies a full week - 'with the intention of capturing it on Shabbos'. ²

Rashi #1: It teaches us that one may not lay siege to a town within three days of Shabbos'. ¹

Rashi #2: It teaches us that one offers the enemy peace terms two ² or three days before going into battle.

Rashi: It is talking about a Milchemes ha'R'shus (an optional war), not a Milchemes Mitzvah. ¹

Sifri: It implies that the prohibition applies only if the intention is to capture the town, but not if one intends to destroy it - in which case it is permitted to cut down the fruit-trees. ¹

Destroying a fruit-tree - or rendering useless anything that is initially useful falls under the category of 'Bal Tashchis'. ¹ Consequently, even someone who tears K'riyah on a Meis more than is necessary ² transgresses.

Makos, 22b: "ve'Oso Lo Sichros" is a La'av against cutting down good trees ¹ (and "Lo Sachchis" teaches us that if one benefits more by cutting it down, ² - 'Bal Tashchis de'Gufa Adif' - it is permitted - Shabbos, 129a).

Rashi: It refers to all fruit-trees that grow on the outskirts of the town.

Ramban: It refers to destroying fruit-trees for the purpose of laying siege - assuming barren trees are available. ¹

Rashbam: It is referring to fruit-trees that grow far away ² from the town under siege.

Da'as Zekenim, Hadar Zekenim and Rosh: The Torah prohibits destroying all fruits trees, except for those among which people can hide to ambush the besiegers.

Seforno: It implies that the prohibition is confined to where one is destroying the tree in order to harm the town's inhabitants, and not for any tactical reasons. ¹

Refer to 20:19:7:1.

Sifri: To add an Asei, so that someone who cuts down a fruit-tree transgtresses an Asei and a Lo Sa'aseh. ¹

Rashi and Targum Yonasan: The Torah is asking 'Is a tree of the field perhaps a human-being - that it needs to be chastised with pangs of hunger and thirst like the inhabitants of the town? So why do you need to destroy it'?

Ramban (citing the Ibn Ezra) and Hadar Zekenim: The Pasuk is missing the word 'Chayei' ¹ and therefore reads 'Ki Chayei ha'Adam Eitz ha'Sadeh'. ²

Seforno: 'Is a tree of the field a human-being that needs to come under siege, in order to force its hand to surrender to you? ³

Da'as Zekenim: The Pasuk must be rearranged. What it means is that trees are for man to eat, and not to destroy them in order to create a siege.

Oros ha'Gra (p.46, citing Agadah of Rabah bar bar Chanah Akrokasa): "Eitzah" are those who support Chachamim. "Mimenu Socheil"

Ramban, Seforno and Rashbam: It implies that, since you are bound to be victorious and will ultimately eat their fruit, you may not cut them down (merely to harm the inhabitants, bearing in mind that chopping down the trees will not force them to surrender

Rashbam: Refer to 20:19:1:2 & 20:19:4:2*.

Targum Yonasan: It enables the attacking army to encircle the town.

Rashi (in Melachim 2 3:19, citing Bamidbar Rabah): That is was Hashem - who detests Mo'av -commanded us in Ki Seitzei, 23:7 "Lo Sidrosh Shelomam ve'Tovasam le'Olam", which includes taking from them "Tovasam" - their trees (whereas "Lo Sashchis" pertains to other nations - Moshav Zekenim).

R'dak (in Melachim 2, 3:19): According to the simple meaning of the Pasuk, the prohibition applies exclusively to the time of the siege - even though a tradition always forbids it. Perhaps the command in Melachim was a Hora'as Sha'ah (a once-off ruling).