What is the opinion of Shi’ah scholars regarding the establishment of Khalafah?

The Shi’ah believe that the Khalafah must be held by the 12 error-free Imams from the
progeny of Prophet Muhammad (PBUH). This belief is based on many authentic ahadith. Therefore, all the Ummayads, Abbasids and Ottomans were ordinary leaders who ran their states according to the standards of their times.
During the First World War, Shi’ah scholars – ulama – supported the Ottomans in their fight with the British on the grounds that the Ottomans were Muslim and the latter were non-Muslim.
This however did not in any way imply unconditional support of the Ottomans as Khalifahs
of the Prophet (PBUH).