Gabriel launched a military campaign against Wallachia on 26 December. Radu Şerban fled the country, enabling Gabriel to take possession of Târgoviște without resistance. Gabriel styled himself prince of Wallachia in a 26 January 1611 charter. According to Radu Popescu's chronicle, his troops brought pillage, destruction and death to the countryside. Gabriel sent his envoys to Istanbul, asking Ottoman Sultan Ahmed I to confirm his rule in Wallachia. He outlined a plan for the conquest of Poland. He also demanded compensation for the salaries of his Hajdús from the Ottomans, who began to call him ""Deli Kiral"" (Mad King) because of his actions.