Several treaties were negotiated at Locarno; they all go together and are to a certain extent mutually dependent. At Locarno, Germany negotiated five treaties: (a) the Treaty of Mutual Guarantee between Germany, Belgium, France, Great Britain, and Italy (TC-12); (b) the Arbitration Convention between Germany and France; (c) the Arbitration Convention between Germany and Belgium; (d) the Arbitration Treaty between Germany and Poland; and (e) an Arbitration Treaty between Germany and Czechoslovakia.
Article 10 of the Treaty of Mutual Guarantee (TC-12) provided that it should come into force as soon as ratifications were deposited at Geneva in the archives of the League of Nations, and as soon as Germany became a member of the League of Nations. The ratifications were deposited on 14 September 1926, and Germany became a member of the League of Nations.
The two arbitration conventions and the two arbitration treaties provided that they shall enter into force under the same conditions as the Treaty of Mutual Guarantee. (Article 21 of the arbitration conventions and Article 22 of the arbitration treaties.)
The most important of the five agreements is the Treaty of Mutual Guarantee (TC-12). One of the purposes was to establish in perpetuity the borders between Germany and Belgium, and Germany and France. It contains no provision for denunciation or withdrawal therefrom and provides that it shall remain in force until the Council of the League of Nations decides that the League of Nations ensures sufficient protection to the parties to the Treaty—an event which never happened in which case the Treaty of Mutual Guarantee shall expire one year later.
The general scheme of the Treaty of Mutual Guarantee is that Article 1 provides that the parties guarantee three things: the border between Germany and France, the border between Germany and Belgium, and the demilitarization of the Rhineland.
Article 2 provides that Germany and France, and Germany and Belgium agree that they will not attack or invade each other, with certain inapplicable exceptions; and Article 3 provides that Germany and France, and Germany and Belgium agree to settle all disputes between them by peaceful means. (TC-12)
The first important violation of the Treaty of Mutual Guarantee appears to have been the entry of German troops into the Rhineland on 7 March 1936. The day after, France and Belgium asked the League of Nations Council to consider the question of the German reoccupation of the Rhineland and the purported repudiation of the treaty. On 12 March, after a protest from the British Secretary for Foreign Affairs, Belgium, France, Great Britain, and Italy recognized unanimously that the reoccupation was a violation of this treaty. On 14 March, the League Council duly and properly decided that reoccupation was not permissible and that the Rhineland clauses of the pact were not voidable by Germany because of the alleged violation by France in the Franco-Soviet Mutual Assistance Pact.
That is the background to the treaty. The relevant articles are 1, 2, and 3, already mentioned; 4, which provides for the bringing of violations before the Council of the League, as was done; and 5, which deals with the clauses of the Versailles Treaty already mentioned. It provides:
“The provisions of Article 3 of the present Treaty are placed under the guarantee of the High Contracting Parties as provided by the following stipulations:
“If one of the Powers referred to in Article 3 refuses to submit a dispute to peaceful settlement or to comply with an arbitral or judicial decision and commits a violation of Article 2 of the present Treaty or a breach of Article 42 or 43 of the Treaty of Versailles, the provisions of Article 4 of the present Treaty shall apply.” (TC-12)