Well I mean the changing nature of the caliphate can be seen in the way it went from elective to hereditary from rashidun to Umayyad. There’s also the weakening of the legal idea that only the caliph can declare jihad and negotiate truces with non Muslim states as time goes on and these rights are taken up more by local leaders and dynasties, from the mid abbasids onwards I think, though I’m not sure on the exact timing, especially the Mamluks later on. And then in the colonial era that morphs into a direct refutation of al ghazalis ideas about tyranny being better than anarchy and turning jihad from something that any established Muslim leader can declare into something that any individual can start.
1. Al-Ghazali, is not someone who is the arbiter regarding the fiqh issues, and there are many disagreements that scholars preceding him and after him had with his views and methodology. While he is certainly not deviant in my view and widely accepted, any statement of his that is given, must be vetted by existing scholars in our records and then vetted toward what we have learned by holy tradition. As a precursor, I am not exactly sure what al-Ghazali refers to when he says that only the Caliph may declare jihad, there is an argument that this may be the case, but it is also generally accepted that the declaration of jihad is not declared truly by a ruler, but by Allah Himself by Divine Command, the Caliph or ruler only has rights to make treaties, deals and such based upon the necessity of the time. Jihad generally is not simply thus a war or treaty, but an existing state of baraa (enmity) with the world around yourself in the sense that Allah has commanded His followers to reject much of this world and some of this includes a command that ultimately one pursues a state of enmity with the kuffar entities that are disobedient and to bring them to heel. In that respect, there is both war and treaties, both are methods of jihad and used tactically for the uses of the Islamic regime. If al-Ghazali said, jihad is only declared by the Caliph, then I would have to disagree with him and nearly all scholars would as well, as this statement would require him to say that Allah is the Caliph, which is kufr akbar (great sin).
Much of this issue is, al-Ghazali was likely influenced by Platonism and other such ideas when he stated this regarding tyranny vs anarchy, not necessarily Islamic traditions, which favored more decentralized warfare. In the Abbasid Caliphate, the Caliphs allowed armies on its fringes, as the Umayyad and Rashidun did, prosecute wars of 'movement', which were in essence, decentralized wars occurring at all ends of the growing Islamic world, as it was understood, all nations and people are ultimately to be attacked or subjugated to a degree and if they cannot be, seek peace in order to by one's time. This situation was generally the case and was accepted as a system with its model directly in the directives of Muhammad (SAW) by all four of the founders of the major 4 madhab. In fact, the Abbasid system allowed the Abbasid to delegate wars of invasion and conquest to other Muslim, as Caliph Abu Bakr did with Khaled bin Walid of Caliph Umar did with his generals, there was never this sort of Byzantine platonism within the Islamic tradition. There is thus not structure by which we say in Islamic jurisprudence, that the state must be a centralized entity, if it is, then this is permissible, if not, then that too is permissible. It should also be remembered, in terms of title, other than the Umayyads in Iberia and some other non Sunni realms, all Muslim states prior to the Fatimids were legally speaking subjects of the Abbasid Caliphate and likewise, so were the Saljuq, Ghaznavids, etc...
2. In terms of the status of al-Ghazali saying only rulers can declare a war, this is true, but declaration of jihad, like I said, is not controlled by a ruler and the Abbasid caliph, in the views of the times, had already legislated wars upon all enemies on its borders, so any individual army under the sponsorship of the Abbasid throne that attacks nearby kuffar, this was in fact a war declared by the ruler. Even in the earliest times, during the Caliphate of Umar, governors of conquered territories were allowed to prosecute military jihad at their own discretion.
"Jihad (physical) is an obligation upon the community; if some people undertake this, the rest are relieved of the obligation." -Ibn Qadamah al-Maqdisi 1147-1223
-This could even include the Caliph^ who centered within the heart of the Islamic world, is not near the kuffar and is difficult for himself to lead the wars personally each time. Thus, it is permissible for him to delegate this function to men who reside on the fringes and have less duties as the Caliph, who concerns himself with enforcing Shari'a.
"Listen and obey, even if you are ruled by an Abyssinian slave." -Prophet Muhammad (SAW)
-This Abyssinian slave, who a Muslim, is your local leader and declares jihad on the fringes, one should still go to perform the jihad. This slave mentioned by the Prophet, is not the Caliph or descended from the Hashim, but Muhammad (SAW) clearly used a term not of his own he held, Caliph, meaning, it is not only him who declares the physical jihad in the moment. If even Muhammad (SAW) delegates to a degree, then that shows you the position of al-Ghazali, if he truly believed this.
"-It should be noted that appointing a leader to run the people’s affairs is one of the greatest of religious duties, without which no religious or worldly matters can be established, because the best interests of the son of Adam cannot be achieved without coming together, because they need one another. When they come together, it is essential to have a leader. The Prophet (peace and blessings of Allaah be upon him) said: “If three people set out on a journey, let them appoint one of them in charge.” Narrated by Abu Dawood from the hadeeth of Abu Sa’eed and Abu Hurayrah. Imam Ahmad narrated in his Musnad from ‘Abd-Allaah ibn ‘Amr that the Prophet (peace and blessings of Allaah be upon him) said: “It is not permissible for three people to be in the wilderness without appointing one of them in charge.” The fact that it is obligatory to appoint one person in charge of a small temporary group whilst travelling indicates that this is essential in all kinds of groups. And Allaah has commanded us to enjoin what is good and forbid what is evil, which can only be achieved from a position of strength and authority, and the same applies to all the other things that He has enjoined, such as jihad, justice, establishment of Hajj, Jumu’ah and Eid, as well as supporting those who are wronged or oppressed, and carrying out hadd punishments – it cannot be achieved except from a position of strength and authority. Hence it was narrated that “the ruler is the shadow of Allaah on earth” and “Sixty years with (even) an unjust ruler are better than one night without a ruler." Experience proves that this is so.-" -Ibn Taymiyyah 1263-1328
- Essentially, even if three people are alone in the wilderness, they may appoint a leader among themselves and conduct their actions, without the necessary need of the Caliph. Further, the Caliph in the situation of the Abbasid has appointed his own rulers to prosecute wars he has set parameters fro or given them freedom to conduct on their own with knowledge best of the surrounding situation. It makes little sense for in an age of hard travel, for the ruler to direct the wars in a mircomanaging fashion in far off Sindh.
In this regard, I am not so puritanical as you portray al-Ghazali and accept that in differing situations, the Caliphate may adopt different methods for what it is required to do.
3. Regarding the election, this is an area of dispute. While Abu Bakr was elected by the people of high position or of great skill, the situation was changed when Abu Bakr appointed Umar al-Khattab as his successor, in this regard, the Abbasid and Umayyad practiced this form of transfer. If Caliph Abu Bakr could appoint his successor, then so could the Abbasid caliphs. If you believe that the appointing of the next caliph by the previous is a nullification of caliphate, then you must also say that the caliphate of Umar al-Khattab is null and only returns to the Caliphate with Utham ibn Affan.