Most historians mark the Greek landing at Smyrna on 15 May 1919 as the start date of the Turkish War of Independence as well as the start of the Kuva-yi Milliye Phase. The occupation ceremony from the outset was tense from nationalist fervor, with Ottoman Greeks greeting the soldiers with an ecstatic welcome, and Ottoman Muslims protesting the landing. A miscommunication in Greek high command lead to an Evzone column marching by the municipal Turkish barracks. The nationalist journalist Hasan Tahsin fired the "first bullet" at the Greek standard bearer at the head of the troops, turning the city into a warzone. Süleyman Fethi Bey was murdered by bayonet for refusing to shout "Zito Venizelos" (meaning "long live Venizelos"), and 300–400 unarmed Turkish soldiers and civilians and 100 Greek soldiers and civilians were killed or wounded.

Greek troops moved from Smyrna outwards to towns on the Karaburun peninsula; to Selçuk, situated a hundred kilometres south of Smyrna at a key location that commands the fertile Küçük Menderes River valley; and to Menemen towards the north. Guerilla warfare commenced in the countryside, as Turks began to organize themselves into irregular guerilla groups known as Kuva-yi Milliye (national forces), which were soon joined by deserting Ottoman soldiers. Most Kuva-yi Milliye bands were between 50 and 200 people strong and were led by known military commanders as well as members of the Special Organization. The Greek troops based in cosmopolitan Smyrna soon found themselves conducting counterinsurgency operations in a hostile, dominantly Muslim hinterland. Groups of Ottoman Greeks also formed Greek nationalist militias and cooperated with the Greek Army to combat Kuva-yi Milliye within the zone of control. What was intended as an uneventful occupation of the Vilayet of Aydin soon became a counterinsurgency.

The reaction of Greek landing at Smyrna and continued Allied seizures of land served to destabilize Turkish civil society. The Turkish bourgeoisie trusted the Allies to bring peace, and thought the terms offered at Mudros were considerably more lenient than they actually were. Pushback was potent in the capital, with 23 May 1919 being largest of the Sultanahmet Square demonstrations by Turks in Constantinople against the Greek occupation of Smyrna, the largest act of civil disobedience in Turkish history at that point.