In an attempt to reduce its economic dependence on the Austro-Hungarian Empire, Seribia began (1904) to import French rather than Austrian munitions and established (1905) a customs union with Bulgaria, making tariff-laden Austrian goods unsalble in Serbia. Long used to setting economic policy, Austria responded in 1906 by closing its borders to Serbian pork. Serbia refused to bow to Vienna, gained French investment to build new packing plants for international trade, began to order materials from the Austrian rival Germany, and pressured the Austrian-administrated provinces of Bosnia and Herzegovina for a trade outlet on the Adriatic Sea. Russia supported Serbia's actions, and war between Austria-Hungary and Russia was averted only because of a German ultimatum (1909) demanding the cessation of Russian aid to Serbia. Serbia and Austria developed a new commercial treaty (1909), but Serbia covertly stirred up trouble among the southern Slavs in newly Austrian-annexed Bosnia and Herzegovina, actions that contributed to the start of World War I.