With the declaration of war, the Greek Army of Thessaly under Crown Prince Constantine advanced to the north, successfully overcoming Ottoman opposition in the fortified Straits of Sarantaporo. After another victory at Giannitsa on , the Ottoman commander Hasan Tahsin Pasha surrendered Thessaloniki and its garrison of 26,000 men to the Greeks on . Two Corps HQs (Ustruma and VIII), two Nizamiye divisions (14th and 22nd) and four Redif divisions (Salonika, Drama, Naslic and Serez) were thus lost to the Ottoman order of battle. Additionally, the Ottoman forces lost 70 artillery pieces, 30 machine guns and 70,000 rifles (Thessaloniki was the central arms depot for the Western Armies). The Ottoman forces estimated that 15,000 officers and men had been killed during the campaign in Macedonia, bringing total losses up to 41,000 soldiers. Another direct consequence was that the destruction of the Macedonian Army sealed the fate of the Ottoman Vardar Army, which was fighting the Serbs to the north. The fall of Thessaloniki left it strategically isolated, without logistical supply and depth to manoeuvre, ensuring its destruction.