When the Ottoman Empire joined World War I on the side of the German Empire in October 1914, Mustafa Kemal was still serving in Sofia. Following the start of the war, his appointment as an attaché was put to an end in January 1915, and he was posted to Tekirdağ (on the Sea of Marmara) with the task of organizing the 19^th Division.

He was later promoted to the rank of Colonel and assigned the command of the newly formed 19^th Division in the Gallipoli () area, under the command of Marshall Otto Liman von Sanders. He played a critical role in the battle against the allied British, French and ANZAC forces during the Battle of Gallipoli in April 1915, where he held off allied forces at Conkbayırı and on the Anafarta hills. For this success, he was later promoted to the rank of Brigadier General, thus acquiring the title of Pasha and gained increasingly greater degrees of influence on the war effort.

Mustafa Kemal gained much respect from his former enemies for his chivalry in victory, the Mustafa Kemal Atatürk Memorial has an honoured place on ANZAC Parade in Canberra. It includes his words:

At the end of World War I, Ottoman Empire suffered the loss of a large amount of territory. Following the end of the war, the Treaty of Sèvres signed between the Ottomans and the Allies further set up the occupation of Anatolia, the remaining core of the Ottoman state, by English, Italian, French and Greek forces, leaving merely a part of Central Anatolia as the Turkish land.

The occupations were met with opposition by Turkish revolutionaries, including numerous local militant resistances and many organized unions of opposition. Public meetings with significant participation were organized, like the Sultanahmet Meetings of 1919 and 1920, during which Halide Edip Adıvar addressed her renowned speech to a crowd of two hundred thousand people. Under these circumstances, Mustafa Kemal became the leading figure of the most successful of several "Kuva-i Milliye" (National Force) movements that blossomed into the Turkish War of Independence.

Mustafa Kemal's revolution began with his assignment in Samsun, where he was given emergency powers as Inspector of the 9^th Army. Once in Anatolia, interpreting his powers liberally, he contacted and started issuing orders to provincial governors and military commanders - calling on them to resist occupation. In June 1919 he and his close friends issued the Declaration of Amasya which described why Istanbul's authority was illegitimate. The Young Turks politically promoted the idea that a government-in-exile should be set up somewhere in Anatolia. Istanbul's order for the execution of Kemal came too late. He resigned from the Ottoman Army in Erzurum which had been the gateway and portal to Turkish tribes migrating to Eastern Anatolia, was declared the "Honorary Native", the freeman of the city, of Erzurum that issued him his first citizenship registration and certificate (Nufus Cuzdani) of the new Republic. A new parliament, the Grand National Assembly, was formed in Ankara in April 1920. It conferred upon Mustafa Kemal Pasha the title 'President of the National Assembly', repudiated the Sultan's government in Istanbul and rejected the Treaty of Sèvres. (For more details on this topic, see Jurisdictional Conflict)

Meanwhile, the conflict between nationalist movement and Triple Entente powers went on three fronts. One of these was the front with Greece (west front), where Turkish forces fell back in good order to the Sakarya river, eighty kilometres from the Grand National Assembly. Atatürk took personal command and decisively defeated the Greeks in the twenty day Battle of Sakarya in August-September 1921. Final victory over the Greeks came in the Battle of Dumlupınar in August 30, 1922. (For more details on this topic, see Theatres of the War)

On the political front, Mustafa Kemal Pasha signed the Treaty of Kars (October 23, 1921) with the Soviet Union - a treaty of friendship in which Turkey ceded the city of Batumi, in present-day Georgia - to Lenin's Bolsheviks in return for sovereignty over the cities of Kars and Ardahan, which were lost to Tsarist Russia in Russo-Turkish War, 1877-1878. (For more details on this topic, see Stage for Peace)

Atatürk once stated: "Culture is the foundation of the Turkish Republic." His view of culture included both his own nation's creative legacy and what he saw as the more admirable values of world civilization, and he put an emphasis on humanism above all. He once described modern Turkey's ideological thrust as "a creation of patriotism blended with a lofty humanist ideal."

So as to assist in the creation of such a synthesis, Atatürk stressed the need to utilize the elements of the national heritage of the Turks and of Anatolia, including its ancient indigenous cultures as well as the arts and techniques of other world civilizations, both past and present. He emphasized the study of earlier Anatolian civilizations, such as the Hittites, Phrygians, and Lydians. The pre-Islamic culture of the Turks became the subject of extensive research, and particular emphasis was laid upon the fact that, long before the Seljuk and Ottoman civilizations, the Turks had had a rich culture. Atatürk also stressed the folk arts of the countryside as a wellspring of Turkish creativity.

The visual and the plastic arts, whose development had on occasion been arrested by some Ottoman officials claiming that the depiction of the human form was idolatry, were highly encouraged and supported by Atatürk, and these flourished in the new Turkish republic. Many museums were opened; architecture began to follow modern trends; and classical Western music, opera, and ballet, as well as the theatre, also took greater hold. Several hundred "People's Houses" and "People's Rooms" across the country allowed greater access to a wide variety of artistic activities, sports, and other cultural events. Book and magazine publications increased as well, and the film industry began to grow.