The preamble to the fourth Hague Convention of 1907 has become known as the de Martens clause, after its author. The clause has been duplicated and adopted in nearly all the major 20th century treaties of the laws of war. The nuclear weapons states consider themselves bound by the clause. It states as follows: "Until a more complete code of the laws of war has been issued, the high contracting Parties deem it expedient to declare that, in cases not included in the Regulations adopted by them, the inhabitants and belligerents remain under the protection and the rule of the principles of the law of nations, as they result from the usages established among civilized people, from the laws of humanity, and the dictates of the public conscience."
The main body of the Hague Conventions reaffirmed and expanded what is stated in the St. Petersberg Declaration in 1868:
It expanded and forbade:
It also went further by prohibiting:
The Hague Conventions reaffirmed that religious, artistic, scientific or charitable buildings should be spared as much as possible during a siege, as well as historical monuments and places where the sick and wounded are cared for.
By Hague Convention V, the territory of neutral powers was made inviolable3
3 Article 1, Convention (V) Respecting the Rights and Duties of Neutral Powers and Persons in Case of War on Land.