The word 'caliph' is the English form of the word 'khalifa', which means successor of the messenger of God after Muhammad. The first four caliphs are Abu bakr, umar, uthamn and Ali.

The role that Abu bakr played as one of the four caliphs was pretty important. Abu bakr was Muhammad's closest companion and once Muhammad passed away in 632 ad, the Islamic world needed a new leader, so the companions of the prophet who assembled in order to select a new leader. It became apparent to the companions that no one was more suited to the role than Abu bakr.

This man that had the burden of leading the Islamic community though their most sensitive period of their existence, during the leader Muhammad's passing. During the mourning, people in the Islamic community refused to pay zakat due to Muhammad's death. Others In The community claimed that Allah has passed on the prophethood on to them after Muhammad's death and that they were threatening to revolt and riot against the companions of the prophet. There has also been external threats from Persians and from Rome.

Many of the companions including umar, asked Abu bakr for concessions for the people that refuse to pay zakat. Abu refused claiming that the law cannot be divided and that any compromise with the law of God will rot out the foundations of Islam. The tribes that are revolting assembled to attack Mecca, but the companions were ready for them. Abu bakr himself led the charge against the revolting tribes and made them retreat. Abu bakr declared war on the impostors which made most of the impostors submit and profess to Islam again.

Another contribution of Abu Bakr to the cause of Islam was the collection and compilation of the verses of the Qur'an.

Abu bakr only had a two year reign before he died, but The contribution Abu bakr gave to the Islamic community was significant. He led the Islamic community though a very rough patch in in the history of the Islamic community with the passing of the prophet Muhammad. Abu bakr has brought peace to the disturbed Islamic community by taking up the responsibility of leading the Islam nation to peace and harmony, he has also secured the Islamic people from the perils which has threatened their own existence.

The role that umar played as one of the four caliphs was pretty significant. After the death of Abu bakr, umar was quickly put into power due to him being born in the quraysh tribe thirdteen years after Muhammad was born. Umar was only twenty seven when Muhammad proclaimed his mission to the world. This enraged umar due to umar coming for a merchant family.

The most notable feature of umar's caliphate was the vast expansion of Islam. Apart from Arabia, Egypt, Iraq, Palestine and Iran also came under the protection of the Islamic government. But the greatness of umar himself lies in the quality of his rule.

The role that uthaman played as one of the four caliphs was pretty significant. During his rule, he carried on with what Abu bakr and umar has done with the expansion of Islam, impartial justice for everyone. During his rule, uthaman crated the Islamic navy to go along with the Islamic army. He also organised the administrative divisions around the Islamic empire and expanded and completed many public projects. The biggest contribution that uthaman gave to Islam is compiling a complete and authoritive text of the Quran. Massive numbers of the Quran were sent out over the Islamic world.

Uthamn ruled for twelve years, the first six years was full of peace, the second half was full or rebellions against uthaman. Uthaman tried to reason with the rebels but they broke into his compound and murdered him.

The contribution that uthaman gave to Islam was pretty significant. He made up the Islamic navy which can go to the far reaches of the globe to spread the word of Allah and that he made large amounts of copies of the Quran to go out over the Islamic empire.

The role that Ali played as one of