During these years, Heraclius strove to rebuild his army, slashing non-military expenditures, devaluing the currency and melting down Church plate, with the backing of Patriarch Sergius, to raise the necessary funds to continue the war. In 622, Heraclius left Constantinople, entrusting the city to Sergius and general Bonus as regents of his son. He assembled his forces in Asia Minor and, after conducting exercises to revive their morale, he launched a new counter-offensive, which took on the character of a holy war.* Cameron (1979), 23; Grabar (1984), 37</ref> In the Caucasus he inflicted a defeat on an army led by a Persian-allied Arab chief and then won a victory over the Persians under Shahrbaraz.* Greatrex–Lieu (2002), II, 199</ref> Following a lull in 623, while he negotiated a truce with the Avars, Heraclius resumed his campaigns in the East in 624 and routed an army led by Khosrau at Ganzak in Atropatene.* Greatrex–Lieu (2002), II, 199–202</ref> In 625 he defeated the generals Shahrbaraz, Shahin and Shahraplakan in Armenia, and in a surprise attack that winter he stormed Shahrbaraz's headquarters and attacked his troops in their winter billets.* Greatrex–Lieu (2002), II, 202–205</ref> Supported by a Persian army commanded by Shahrbaraz, together with the Avars and Slavs, the three unsuccessfully besieged Constantinople in 626,* Cameron (1979), 5–6, 20–22</ref> while a second Persian army under Shahin suffered another crushing defeat at the hands of Heraclius' brother Theodore.McBride (2005), 56</ref>