When World War I broke out in 1914, Mahmud Pasha opposed the Ottoman participation in view of the unpreparedness of the armed forces.

In 1914, Mahmud Pasha's candidacy was put forward by the Sultan to serve in the Ottoman Senate (Ayan Meclisi).

After the defeat of the Ottoman Empire in WW I, Mahmud Pasha led the commission to negotiate peace.

Mahmud Pasha's support for territorial concessions to reach an agreement with Armenians in 1919 drew criticism from Mustafa Kemal Atatürk.

Upon their repatriation in 1921, he returned to Turkey and joined the forces of Mustafa Kemal Atatürk to take part in the Turkish War of Independence.