increased by 30 per cent and iron output increased by 38 per cent from 1913. Keynes predicted that German coal extraction would also decrease and that Germany would not be able to export coal immediately after the war. Mantoux also counters these arguments. By 1920, German was exporting 15 million tons of coal a year and reached 35 million tons by 1926. By 1929, German coal mining had risen by 30 per cent on the 1913 figures because of her increased labor efficiency methods. In regard to national savings, Keynes stated that 2 billion marks would only be possible after the adoption of the treaty. Mantoux says that the 1925 German national savings figure was estimated at 6.4 billion marks, rising to 7.6 billion marks by 1927. Mantoux calculated that Germany borrowed between 8 billion and 35 billion marks in the period 1920–1931, while only paying 21 billion in reparations. This, he says, allowed Germany to re-equip, expand, and modernize her industry. Highlighting the rearmament under Hitler, Mantoux said Germany "had been in a stronger position to pay reparations than Keynes had made out". He also says that Germany could have paid all of the reparations if she had wanted to, and that the problem was not that Germany was unable to pay, but that she was unwilling to pay. In 1954, United States Secretary of State John Foster Dullesone of the authors of Article 231said that, "Efforts to bankrupt and humiliate a nation merely incite a people of vigor and of courage to break the bonds imposed upon them ... Prohibitions thus incite the very acts that are prohibited." Modern Geoff Harcourt writes that Keynes' arguments that reparations would lead to German economic collapse have been adopted "by historians of almost all political persuasions" and have influenced the way historians and the public "see the unfolding events in Germany and the decades between Versailles and the outbreak of the Second World War". He says Mantoux's work "is not simply a critique of Keynes", but "a stimulus to question the received wisdom's interpretation of the unfolding events in Germany". Harcourt says that despite it discussing Keynes' errors "in great detail", Mantoux's work "has not led us to revise our general judgment of Keynes", yet "it does make us question the soundness of theoretical and empirical aspects" of his arguments. A.J.P. Taylor writes that in 1919 "many people believed that the