After an ideological transformation, from 1913 to 1918, the CUP ruled the empire as a dictatorship[26][27] and committed genocides against the Armenian, Greek, and Assyrian peoples as part of a broader policy of ethnic erasure during the late Ottoman period.

With the help of their paramilitary, the Special Organization, the Unionist régime enacted policies resulting in the destruction and expulsion of the empire's Armenian, Pontic Greek, and Assyrian citizens in order to Turkify Anatolia.

Following Ottoman defeat in World War I in October 1918, CUP leaders escaped into exile in Europe, where the Armenian Revolutionary Federation assassinated several of them (including Talât and Cemal) in Operation Nemesis in revenge for their genocidal policies.

Ahmet Rıza, being an avid follower of Auguste Comte and his theories on progressivism, changed the name of the early club to the Committee of Union and Progress (CUP) (Ottoman Turkish: اتحاد و ترقى جمعيتی, romanized: İttihad ve Terakki Cemiyeti).

[33] The Committee of Ottoman Union (İttihad-ı Osmanî Cemiyeti) was established as a secret society on 2 June 1889 by Ibrahim Temo, Dr. Mehmed Reşid, Abdullah Cevdet, and İshak Sükuti, all of whom were medical students of the Imperial Military School of Medicine in Constantinople.

They met every Friday in different places, where they held seminaries discussing the works of Young Ottoman thinkers such as Namık Kemal and Ziya Pasha, drafted regulations, and read banned philosophy and literature.

The minority turned out to be more ideologically cohesive, so Rıza formed a coalition with the Activists and founded the Committee of Progress and Union (CPU, Osmanlı Terakki ve İttihat Cemiyeti), and now endorsed a "legitimate" revolution.

After the Young Turk Revolution, this "Macedonian"cadre, consisting of Talât, Şakir, Doctor Nâzım, Enver, Ahmed Cemal, Midhat Şükrü, and Mehmed Cavid supplanted Rıza's leadership of the exiled Old Unionists.

[57] Under this umbrella name, one could find ethnic Albanians, Arabs, Armenians, Aromanians, Bulgarians, Serbians, Jews, Greeks, Turks, and Kurds, united by the common goal of overthrowing Abdul Hamid II's despotic regime.

[58] On 22 December 1907, in the Second Congress of Ottoman Opposition [tr], Rıza, Sabahaddin, and the Dashnaks were finally able to put their differences aside and signed an alliance, declaring that Abdul Hamid had to be deposed and the regime replaced with a representative and constitutional government by any means necessary, without foreign interference.

[30] Much to the committee's dismay, the instability during the revolution resulted in more territorial loses for the Empire, which would not be reversed due to the European powers refusing to uphold the status quo set by the Treaty of Berlin.

[65] The CUP decided to continue its clandestine nature by keeping its membership secret but sent to Constantinople a delegation of seven high-ranking Unionists known as the Committee of Seven, including Talât, Cemal, and Cavid to monitor the government.

[65] A separate parliamentary group from the committee was created, known as the Union and Progress Party (Ottoman Turkish: إتحاد و ترقى فرقه‌ سی, romanized: İttihad ve Terakki Fırkası), whose membership was open to the public.

[88] A great many officers, most of whom Unionist, including Enver, his younger brother Nuri, Mustafa Kemal, Süleyman Askerî, and Ali Fethi (Okyar) all departed to Libya to fight the Italians.

This proved too little and too late to salvage Rumelia; Albania, Macedonia, and western Thrace was lost, Edirne was put under siege, and Constantinople was in serious risk of being overrun by the Bulgarian army (see First Battle of Çatalca).

Other than the Three Pashas and Halil, éminence grises such as Dr. Nâzım, Bahattin Şakir, Ziya Gökalp, and the party's secretary general Midhat Şükrü at times also dominated the Central Committee without formal positions in the Ottoman government.

[121] As such, the Turks needed to become the dominant political and economic group within the Ottoman Empire while uniting with all of the other Turkic peoples in Russia and Persia to create a vast pan-Turkic state covering much of Asia and Europe.

An extensive purge of the army was carried out, with about 1,100 officers including 2 field marshals, 3 generals, 30 lieutenant-generals, 95 major-generals and 184 colonels whom Enver had considered to be inept or disloyal forced to take early retirement.

[137]The campaign did not proceed with the same level of brutality as did the Armenian genocide during 1915 as the Unionists were afraid of a hostile foreign reaction, but during the "cleansing" operations in the spring of 1914 carried out by the CUP's Special Organisation it is estimated at least 300,000 Greeks fled across the Aegean to Greece.

[151] On 21 October, Enver Pasha informed the Germans that his plans for the war were now complete and he was already moving his troops towards eastern Anatolia to invade the Russian Caucasus and to Palestine to attack the British in Egypt.

[153] After this act of aggression against his country, Sazonov submitted an ultimatum to the Sublime Porte demanding that the Empire intern all of the German military and naval officers in their service; after its rejection Russia declared war on 2 November 1914.

[153] With the expectation that the new war would free the Empire of its constraints on its sovereignty by the great powers, Talât went ahead with accomplishing major goals of the CUP; unilaterally abolishing the centuries-old Capitulations, prohibiting foreign postal services, terminating Lebanon's autonomy, and suspending the reform package for the Eastern Anatolian provinces that was in effect for just seven months.

[166] Deported Armenians had their property confiscated by the state and redistributed to Muslims or simply snatched by local provincial authorities (such as Central Committee member Mehmet Reşid's governorship in Diyarbekir).

When it came to the military, though the withdrawal of Russia from the war and the Treaty of Brest-Litovsk, negotiated and signed by Talât Pasha, was not only a massive success for the CUP but also for the Ottoman-German alliance, it simply delayed conflict.

The Ottoman Empire regained the Caucasian provinces (Batumi, Kars, Ardahan) lost in the war against Russia forty years ago, but nothing was guaranteed for the CUP's Turanist ambitions in the Caucasus and Central Asia.

The new government in the Ottoman Empire, led by Damat Ferid Pasha and Mehmed VI Vahdettin as Sultan, obligingly arrested over 100 Unionist party and military officials by April 1919 and began a series of trials.

CUP Central Committee members Ziya Gökalp, Halil Menteşe, Midhat Şükrü Bleda, Fethi Okyar, and Rahmi Arslan managed to integrate themselves within the new post-Ottoman regime.

Other important Republican Turkish figures formerly associated with the CUP included Rauf Orbay, Kâzım Karabekir, Adnan Adıvar, Şükrü Kaya, Çerkez Ethem, Bekir Sami, Yusuf Kemal, Celaleddin Arif, Ahmet Ağaoğlu, Recep Peker, Şemsettin Günaltay, Hüseyin Avni, Mehmet Emin Yurdakul, Mehmet Akif Ersoy, Celal Nuri İleri, Ali Münif Yeğenağa, Yunus Nadi Abalıoğlu, Falih Rıfkı Atay, and others.

Consequently, both parties were required to be outlawed, although Kazim Karabekir, founder of the PRP, was eventually rehabilitated after the death of Atatürk by İnönü and even served as speaker of the Grand National Assembly of Turkey.

After the Young Turk Revolution, reformist elements in the Greek military formed a secret revolutionary organization modeled from the CUP which overthrew the government in the Goudi Coup, bringing Eleftherios Venizelos to power.