דברים, פרק כ׳, פסוק כ׳

The laws of warfare carefully balance urgent military needs with the preservation of the environment and the local economy. During a prolonged siege, an army requires raw materials to build fortifications and earthworks. However, strict limitations are placed on logging, reflecting a broader prohibition against pointless destruction. Soldiers are permitted to harvest timber, but they may only cut down trees that do not bear fruit.

The definition of a non-fruit tree extends beyond naturally barren species. It includes older, dried-out, or decaying fruit trees that no longer yield enough produce to justify their upkeep [ספורנו, רלב״ג, מלבי״ם, חזקוני], as well as wild forest trees whose fruit is unfit for human consumption [הכתב והקבלה]. Identifying these trees requires careful examination and absolute certainty; if there is any doubt about a tree's potential to produce edible fruit, it must be spared [העמק דבר, קונטרס חיבה יתירה, שטיינזלץ]. When a choice exists, barren trees must always be cut before active fruit trees. Yet, if the timber of a barren tree is exceptionally valuable for construction—worth more than the fruit tree itself—the fruit tree may be cut first [תורה תמימה, אדרת אליהו]. An additional military exception allows for the removal of a productive fruit tree if it grows dangerously close to the city walls, where it might obstruct the army's advance or provide cover for the enemy [רשב״ם, חזקוני].

A clear distinction is made regarding how trees are handled. Maliciously destroying a tree without a practical building purpose, such as cutting off its water supply to dry it out, is strictly forbidden. In contrast, cutting a tree from its roots with an ax is permitted solely when the wood will be put to immediate use [הכתב והקבלה, העמק דבר]. The harvested timber is intended specifically for constructing siege mounds and fortifications to trap the city and prevent the enemy from escaping [הכתב והקבלה, מלבי״ם, ביאור יש״ר]. Nevertheless, while the city remains hostile and under siege, it must not be completely surrounded. One side must remain open, providing an escape route for any inhabitants who choose to flee rather than fight [רלב״ג, ביאור יש״ר].

The siege must be maintained until the city is entirely overcome. Commentators debate the exact nature of this defeat. Many understand it as the political surrender and subjugation of the city and its people [רש״י, מזרחי, נתינה לגר, שפתי חכמים]. Others interpret the defeat more physically, referring to the literal collapse of the city's high, fortified walls [רשב״ם, בכור שור, ביאור יש״ר]. The sheer amount of time required to achieve this victory indicates that the targeted city is exceptionally strong and well-defended [אבן עזרא]. Practically, the instruction to persist until the city falls dictates that once the campaign begins, momentum cannot be broken. The army is permitted to maintain the siege, build fortifications, and continue fighting without interruption, even on the Sabbath [תורה תמימה, רלב״ג, מלבי״ם, בכור שור, אדרת אליהו].