The same reasons which restricted the growth of the political independence of Serbia have also impeded, or rather made impossible, its economic development and material prosperity. Until recent years Austria-Hungary and Turkey between them held Serbia territorially in such a position that whenever Serbia either demurred at its neighbours’ tariffs or wished to retaliate by means of its own, the screw was immediately applied and economic strangulation threatened. Rumania and Bulgaria economically could never be of help to Serbia, because the products and the requirements of all three are identical, and Rumania and Bulgaria cannot be expected to facilitate the sale of their neighbours’ live stock and cereals, when their first business is to sell their own, while the cost of transit of imports from western Europe through those countries is prohibitive. After the unsuccessful rebellion of 1788, already mentioned, Serbia remained in a state of pseudo-quiescence for some years. Meanwhile the authority of the Sultan in Serbia was growing ever weaker and the real power was wielded by local Turkish officials, who exploited the country, looked on it as their own property, and enjoyed semi-independence. Their exactions and cruelties were worse than had been those of the Turks in the old days, and it was against them and their troops, not against those of the Sultan, that the first battles in the Serbian war of independence were fought. It was during the year 1803 that the Serbian leaders first made definite plans for the rising which eventually took place in the following year. The ringleader was George Petrović, known as Black George, or Kara-George, and amongst his confederates was Miloš Obrenović. The centre of the conspiracy was at Topola, in the district of Šumadija in central Serbia (between the Morava and the Drina rivers), the native place of Kara-George. The first two years of fighting between the Serbians and, first, the provincial janissaries, and, later, the Sultan’s forces, fully rewarded the bravery and energy of the insurgents. By the beginning of 1807 they had virtually freed all northern Serbia by their own unaided efforts and captured the towns of Požarevac, Smederevo, Belgrade, and Šabac. The year 1804 is also notable as the date of the formal opening of diplomatic relations directly between Serbia and Russia. At this time the Emperor Alexander I was too preoccupied with Napoleon to be able to threaten the Sultan (Austerlitz took place in November 1805), but he gave the Serbs financial assistance and commended their cause to the especial care of his ambassador at Constantinople.