The first article of this treaty reads:
“The contracting powers recognize that hostilities between them must not commence without a previous and explicit warning in the form of either a declaration of war, giving reasons, or an ultimatum with a conditional declaration of war.” (TC-3)
D. Convention 5, Respecting the Rights and Duties of Neutral Powers and Persons in Case of War on Land, signed at the Hague on 18 October 1907.
Germany was an original signatory to this Convention (TC-4), and the treaty is in force as a result of ratification or adherence between Germany and Norway, Denmark, Belgium, Luxembourg, The Netherlands, the USSR, and the United States.
Article 1 reads:
“The territory of neutral powers is inviolable.” (TC-4)
A point arises on this Convention. Under Article 20, the provisions of the present Convention do not apply except between the contracting powers, and then only if all the belligerents are parties to the Convention.
As Great Britain and France entered the war within two days of the outbreak of the war between Germany and Poland, and one of these powers had not ratified the Convention, it is arguable that its provisions did not apply to the Second World War.
Since there are many more important treaties to be considered, the charge will not be pressed that this treaty was likewise breached. The terms of Article 1 are cited merely as showing the state of International opinion at the time, and as an element in the aggressive character of the war.
E. Treaty of Peace between the Allies and the Associated Powers of Germany, signed at Versailles on 28 June 1919.