In October 1920, the Greek Army advanced east into Anatolia, with the encouragement of British Prime Minister, Lloyd George who intended to increase the pressure on the Turkish and Ottoman governments to sign the Treaty of Sevres. This advance was begun under the Liberal government of Venizelos, however, a war weary electorate voted him out and soon after the offensive began he was replaced by Dimitrios Gounaris, who appointed inexperienced monarchist officers to senior commands. King Constantine assumed personal command of the army at Smyrna. The strategic objective of these operations was to defeat the Turkish Nationalists and force Kemal into peace negotiations. The advancing Greeks met little resistance, as the Turks managed to retreat in an orderly manner and avoid encirclement.The Greek advance was halted for the first time at the first battle of Inonu on January 11, 1921, and the Allied states proposed to amend the Treaty of Sevres at a conference in London where both the Revolutionary and Ottoman governments were represented.
Although some agreements were reached with Italy, France and Britain, the decisions were not agreed to by the Greek government, who believed that they still retained the strategic advantage and could negotiate from a stronger position. The Greeks initiated another attack on March 27 (Battle of İnönü II), to be resisted fiercely and finally defeated by the Kemalist troops on March 30. The British favored a Greek territorial expansion unfortunately, they refused to offer any military assistance in order to avoid provoking the French. The Turkish forces however received significant assistance from the Soviet Union. In June 1921, a reinforced Greek Army advanced to the River Sakarya , 62 miles west of Ankara. Meanwhile, the new Turkish government at Ankara appointed Mustafa Kemal, as commander in chief. The advance of the Greek Army faced fierce resistance which culminated in the 21-day Battle of the Sakarya (August 23 - September 13, 1921). The ranks of the Greek were augmented by Greek volunteers from Asia Minor. These men knew full well the costs of failure and both sides fought valiantly. No quarter was asked and none given. Much of the fighting was close quarters and hand to hand. The ferocity of the battle exhausted both sides to such an extent that they were both contemplating a withdrawal, but the Greeks were the first to withdraw to their previous lines. That was the furthest in Anatolia the Greeks had advanced, and within few weeks they withdrew in an orderly fashion back to the lines they held in June, intending at least to protect the Smyrna area.
The Greek defeat can be largely attributed to a lack of whole-hearted Allied support, as King Constantine was reviled by the British for his pro-German policies during World War I (in contrast to former prime minister Venizelos). On the contrary, the Kemalist Turks enjoyed significant Soviet support. The main reason though was the poor strategic and operational planning of this ill-conceived advance in-depth. Although the Greek Army was not lacking in men, courage or enthusiasm, it was lacking in nearly everything else. Three factors contributed to Greek defeat: poor leadership at the strategic level, replacement of Venizelist officers all the way down to platoon level by inexperienced monarchist officers, and poor logistics.
The Greek Army exceeded the limits of its logistic structure, overextended its supply lines and had no way of retaining such a large territory under constant attacks by regular and irregular Turkish troops fighting in their homeland. Having failed to reach a military solution Greece appealed for allied help, but the allies decided that the treaty of Sevres could not be enforced and they evacuated their positions leaving the Greeks exposed. In March 1922 the Allies proposed an armistice, but Kemal feeling that now he has the strategic advantage, declined any settlement while the Greeks remained in Anatolia and intensified his efforts to re-organize the Turkish military for the final offensive against the Greeks. At the same time, the Greeks strengthened their defensive positions, but were increasingly demoralized by the inactivity of remaining on the defensive and the prolongation of the war. The Turkish offensive was launched on August 26, defeating the Greeks at the Battle of Dumlupınar near Afyon (August 30, 1922), celebrated as "Victory Day" and a national holiday in Turkey.
The Greek Army was thrown back in headlong flight towards Smyrna. Some units were able to remain cohesive and retreated fighting all the way. Others fell apart. It has been suggested that the Greek retreat involved a "scorched earth" policy, which left large tracts of land and property ruined or destroyed. The adherents of this view claim that the burning of crops left the remaining inhabitants of Smyrna close to starvation. However, the validity of this interpretation is questionable considering the haste of the Greek retreat (which was concluded in fewer than 2 weeks), and the lack of any documented evidence of Greek orders to destroy property during the retreat. In any case, most historians today agree that the great fire that gutted Smyrna expanded from the burning of Greek and Armenian Quarters of Smyrna by the Turkish Army. Despite an order from Kemal to prevent harm to non-combatants, these orders were largely ignored, and Nasruddin Pasha, the commander of Turkish forces in the Smyrna district gave orders contradicting Ataturk's. Nasruddin Pasha's orders were largely followed, and the Greek and Armenian civilian population of Smyrna suffered heavily at the hands of the Turkish Army.