After the end of the Third Anglo-Afghan War and the signing of the Treaty of Rawalpindi on 19 August 1919, Emir Amanullah Khan declared the Emirate of Afghanistan a sovereign and fully independent state. He moved to end his country's traditional isolation by establishing diplomatic relations with the international community, particularly with the Soviet Union and the Weimar Republic of Germany. He proclaimed himself King of Afghanistan on 9 June 1926, when the Emirate of Afghanistan became the Kingdom of Afghanistan. Following a 1927–28 tour of Europe and Turkey, he introduced several reforms intended to modernize his nation. A key force behind these reforms was Mahmud Tarzi, an ardent supporter of the education of women. He fought for Article 68 of Afghanistan's 1923 constitution, which made elementary education compulsory. The institution of slavery was abolished in the Emirate of Afghanistan in 1923. King Amanullah's wife, Queen Soraya, was an important figure during this period in the fight for woman's education and against their oppression.