At the turn of the century Warsaw was vital for Russian military planning. The city was headquarters of the westernmost of 14 Russian military districts, and home to a large military garrison. As since the Berlin Congress of 1878 relations with Germany were steadily deteriorating, the area was of growing concern for the Russian General Staff. Itself a prominent salient flanked by German and Austro-Hungarian provinces, it posed a challenge for planners. The prevailing military strategy, known as Miliutin-Obruchev system, pursued a defensive counteroffensive vision; it admitted that initially it might be necessary to abandon territories west of the Vistula and mount a defence based on seven fortresses, of which Warsaw and the other three would form a forward shield.