Abbas I had recently undertaken a major reform of his army through the English gentleman of fortune Robert Shirley and the shah's favorite ghulam and chancellor Allahverdi Khan and thus opened in 1603, with the first Safavid pitched victory won in 1604. This forced the Ottomans to return the territory they had seized from Persia, including Baghdad. He then won another victory at Basra in 1605, soon after extending his empire beyond the Euphrates; forcing the Ottomans to cede back almost all of the Caucasus, Mesopotamia and eastern Anatolia, including recognizing Persian suzerainty of the newly conquered North Caucasian territory of Kabardino-Balkaria, all according to the Treaty of Nasuh Pasha. Hostilities ceased momentarily in 1614 with the Persian army at its peak. Hostilities later resumed and Abbas completely crushed the allied Ottoman-Tartar force near Sultanieh in 1618, bringing the war to an end on terms highly favourable to the Persians.