Explanation: After WW1, the Ottoman Empire was a defeated nation, and the Entente imposed an immensely damaging treaty on the Ottomans. The Ottomans, being battered and not in great fighting shape even to begin with, acquiesced, which resulted in the Ottoman Empire's foreign territories being released, and Turkiye itself being carved up into occupation zones.
One war hero of the Ottoman Empire, a liberal nationalist by the name of Mustafa Kemal, who fought at Gallipoli and was consistently at the head of the few victories the Ottomans did manage to eke out, did not regard this as acceptable, and rallied the defeated nation to save itself from total dissolution. While the French and British were calculating just how much blood and treasure they were willing to spend on subjugating Turkiye, the Greeks eagerly tossed themselves into the cause of forcing the upstart Mustafa Kemal to submit to the will of the Ottoman Sultan who signed the treaty (as the treaty imposed on the Ottoman Empire was very favorable to the Greeks, and the Greeks and Turks have a... long history of enmity).
Mustafa Kemal instead threw the Greeks out of Turkiye, deposed the Sultan, and founded the Republic of Turkiye, which has lasted (if intermittently tormented by instability) to this day. The Brits and French decided, at that point, renegotiating the treaty was an acceptable alternative to fighting a man who could rally a defeated and disarmed nation to eject its occupiers.
Mustafa Kemal would later be granted the name Ataturk by the Turkish legislature, the name by which he is generally known in histories now.