The War of the Bavarian Succession broke out with the invasion of the Prussian Army into Bohemia on 5 July 1778, after Austria and Prussia could not negotiate a solution to their differences. Due to difficulties in supplying the troops, the war became a stalemate: the Prussians were not able to advance far into the Bohemian lands, but the Austrians were unwilling to invade Saxony or Prussia. This was partly because Empress Maria Theresa (the mother of Joseph II and his co-ruler as Queen of Bohemia and Archduchess of Austria) firmly opposed the war after it became clear that a stalemate prevailed. She dispatched peace initiatives to King Frederick II of Prussia and forced her son to accept mediation by France and Russia. The peace came at the initiative of the Russian Empress Catherine the Great and was guaranteed by both Russia and France.