He was a general during World War I and also one of the last Grand Viziers of the Ottoman Empire (14 October 1918 – 8 November 1918) and its last Minister of Foreign Affairs.

In January 1904, he was assigned to suppress the Yemen rebellion as the chief of staff of the Ottoman army, being stationed there for three and a half years.

His strong opposition to Shevket Pasha and von der Goltz led to his dismissal and reappointment to Yemen, to crush another revolt, in February 1911.

During his time in high command, he played a leading role in the modernization of the Ottoman army under the supervision of German military advisors.

When he returned from Yemen on 17 November 1912, he was approached by Mehmed Talaat and Hacı Adil (Arda) to be Grand Vizier after a Unionist putsch.

İzzet Pasha resigned from the War Ministry in January 1914 when he refused to implement army reforms demanded by the CUP.

His government consisted mainly of the anti-war faction of the CUP, including figures such as Mehmed Cavid, Rauf (Orbay), and Fethi (Okyar).

Before his resignation he endorsed plans to form dozens of commissions that would return or compensate the losses of homes and businesses to Ottoman Greek and Armenian deportees.

Afterwards, he was criticized for allowing all three of the Three Pashas to escape abroad on the night of 2–3 November before they could be put on trial in the Turkish Courts-Martial of 1919–20 for crimes including atrocities against the Armenians of the Empire.

İzzet Pasha gave a lukewarm promise of safety to Talat:[10] "As long as I am in the cabinet, I will never turn you over to the enemy.

[12] Under Grand Vizier Ali Rıza Pasha he became a sort of unofficial ambassador for the Ottoman government to the Nationalist Movement, then based in Sivas organized under the Committee of Representation.

He lived on a pension, though in 1934, he was appointed to the board of directors of the Istanbul Electricity Company, which provided him with "a certain amount of peace of mind."

Ahmed İzzet Pasha's decisions during the Caucasus campaign have also been criticized and are regarded as one of the factors of its failure, while his subsequent high reputation in Turkey has been attributed to his successful activity during the Turkish War of Independence.

[14] According to Ali Fuat Cebesoy, İzzet Pasha was highly knowledgeable on military sciences, strategy, philosophy, literature.