Hague Conventions of 1899

Convention (II) with Respect to the Laws and Customs of War on Land and its annex: Regulations concerning the Laws and Customs of War on Land. The Hague, 29 July 1899.

Regulations: Art. 23. Besides the prohibitions provided by special Conventions, it is especially prohibited
(e) To employ arms, projectiles, or material of a nature to cause superfluous injury;

Regulations: Art. 25. The attack or bombardment of towns, villages, habitations or buildings which are not defended, is prohibited.

Gordian Knot(ゴルディアスの結び目)

The cutting of the Gordian Knot is an Ancient Greek legend associated with Alexander the Great in Gordium in Phrygia, regarding a complex knot that tied an oxcart. Reputedly, whoever could untie it would be destined to rule all of Asia. In 333 BC, Alexander was challenged to untie the knot. Instead of untangling it laboriously as everyone expected, he dramatically cut through it with his sword. This is used as a metaphor for inventing an unexpected method to solve a seemingly intractable problem.

Turn him to any cause of policy,
The Gordian Knot of it he will unloose,
Familiar as his garter

Shakespeare, Henry V, Act 1 Scene 1. 45–47