Treadgold cites estimates that indicate the empire's population dropped from 19.5 million in 560 to 10.5 million in 641. At the same time the size of armed forces plunged from 379,300 men to 129,000. By 662, the empire had lost more than half its territory in 30 years, and the first mentions occur in surviving records of themata under the command of generals, or strategi, that are the remnants of the former mobile armies now stationed in set districts. At some later time, when payment in cash had become difficult, the soldiers were given land grants within their districts for their support. The dates of this process are uncertain, but Treadgold points to 659-662 as the most likely time-frame, as this is the period when the Emperor Constans II made a truce with the Arabs that gave the army time to regroup, the government ran out of money to pay the troops, and the empire's enormous losses of territory stopped. The themata so formed provided a bulwark against Arab invasions and raids that lasted until the late 11th century. Themata were also formed in the west, as a response to the Serb and Bulgar incursions that drove the empire's frontier from the Danube River south to Thrace and the Peloponnese. The five original themata were all in Asia Minor and originated from the earlier mobile field armies. They were:  Within each theme, eligible men were given grants of land to support their families and to equip themselves. Following revolts strengthened by the large size of these divisions, Leo III the Isaurian, Theophilus, and Leo VI the Wise all responded by breaking the themes up into smaller areas and dividing control over the armies within each theme into various "tourmai". The large early themes were progressively split up in the 8th–9th centuries to reduce their governors' power, while in the 10th century, new and much smaller themes, called "Armenian themes" because many were settled by Armenians, were created in the East in conquered territories. While in ca. 842 the "Taktikon Uspensky" lists 18 "strategoi" of themes, the "De Thematibus" of ca. 940 lists 28, and the "Escorial Taktikon", written ca. 971–975, lists almost 90 "strategoi" of themes and other military commands. Sicily had been completely lost to the expanding Emirate of Sicily at the beginning of Constantine VII's reign in 905 and Cyprus was a condominium jointly administered with the Abbasid Caliphate until its reconquest by Nikephoros II Phokas in 965.