The serious illness of the Empress, which began with a fainting-fit at Tsarskoe Selo (19 September 1757), the fall of Bestuzhev (21 February 1758) and the cabals and intrigues of the various foreign powers at Saint Petersburg, did not interfere with the progress of the war. The crushing defeat of Kunersdorf (12 August 1759) at last brought Frederick to the verge of ruin. From that day, he despaired of success, but he was saved for the moment by the jealousies of the Russian and Austrian commanders, which ruined the military plans of the allies.