In foreign policy he pursued a policy of détente with Britain, hoping to come to some agreement that would put a halt to the two countries' ruinous naval arms race and give Germany a free hand to deal with France. The policy failed, largely from the opposition of German Naval Minister Alfred von Tirpitz. Despite the increase in tensions because of the Second Moroccan Crisis of 1911, Bethmann Hollweg improved relations with Britain to some extent, working with British Foreign Secretary Sir Edward Grey to alleviate tensions during the Balkan Crises of 1912–1913. He did not learn of the Schlieffen Plan until December 1912, after he had received the Second Haldane Mission. He negotiated treaties over an eventual partition of the Portuguese colonies and the projected Berlin-Baghdad railway, the latter aimed in part at securing Balkan countries' support for a German-Ottoman alliance. The crisis came to a head on 5 July 1914 when the Count Hoyos Mission arrived in Berlin in response to Austro-Hungarian Foreign Minister Leopold Berchtold's plea for friendship. Bethmann Hollweg was assured that Britain would not intervene in the frantic diplomatic rounds across the European powers. However, reliance on that assumption encouraged Austria to demand Serbian concessions. His main concern was Russian border manoeuvres, conveyed by his ambassadors at a time when Raymond Poincaré himself was preparing a secret mission to St Petersburg. He wrote to Count Sergey Sazonov, "Russian mobilisation measures would compel us to mobilise and that then European war could scarcely be prevented."