Muhammad (c.570 - 632) is regarded by Muslims as the greatest and last of a succession of prophets sent by Allah (God). Muhammad's teachings gave rise to the religion of Islam. The Qur'an was allegedly revealed to Muhammad through the angel Gabriel who was sent by God. Muhammad received this revelation over the course of 23 years. While Muslims do not consider Muhammad to be divine, he is held in extreme reverence.
Muhammad was a merchant, religious leader and military general of converts. He claimed to have received a revelation from Allah that there was one monotheistic god. Muhammad spent many years in Mecca attempting to gain converts to his new religion with limited success. Fleeing from persecution in 622, he travelled to Medina with his followers. While based in Medina, he united the surrounding tribes and conducted a war against the Meccan tribes. In 629, Muhammad finally lead an army that captured Mecca and destroyed the pre-existing pagan polytheistic temples and idols. This was followed by various military expeditions against nearby pagan tribes that refused to convert to Islam.  Before his death by illness in 630, most of the Arabian peninsula had converted to Islam.
Muhammad is said to have had thirteen wives, mainly for political or humanitarian reasons. He had several children and grandchildren. He was a slave owner, which was a common practice at the time.
Honorific "Peace be upon him"
Muslims usually append "Peace be upon him", PBUH or the Arabic equivalent after Muhammad's name or any other prophet. This is based on the saying attributed to him by a hadith:
- "The miser is the one in whose presence I am mentioned, then he does not send the Salah [prayer] upon me."
This practice may be ignored by non-believers.
Depiction of Muhammad
Many modern Muslims consider depiction of Muhammad as potentially idolatrous and almost always blasphemous. While there is no explicit ban on depiction in the Qur'an, depicting any prophets is forbidden in a few hadiths. While some sections of Islam are more tolerant of depictions, there are many who believe that no depictions, even by non-believers, are allowed. This is obviously contrary to freedom of expression that is practiced in many non-theocratic countries.
Several writers and artists have been threatened based on their Islamic themed art, such as the still current fatwā and failed assassination attempts targeting Salman Rushdie which forced him into hiding for many years. Another notorious case was the Jyllands-Posten cartoons, which lead to protests and unrest in several middle eastern countries and lead to several deaths. In 2015, gunmen attacked the offices of the French magazine Charlie Hebdo and killed 12 people - mostly journalists. The gunmen were likely motivated by the magazine's depiction of Muhammad in satirical cartoons.  Violence is a gross overreaction to the work of non-violent artists and journalists, as well as being incompatible with freedom of speech and an open society.
Some governments have argued that certain aspects of religion, including criticism or depiction of Muhammad, should be banned on the grounds of religious defamation. This is contrary to the principle of freedom of speech.
Muhammad performed many questionable activities in his life. Criticism of them is sometimes labelled as presentism  and generally avoided by historians. However, if Muhammad claimed to have a timeless objective moral code, it is appropriate to discuss his actions in a contemporary moral context.
Muhammad treated his enemies without mercy, including ordering the beheading of hundreds of surrendered prisoners, assassinations, ordering torture, selling women and children of defeated tribes into slavery and exiling whole tribes. Apologists dispute some of these claims and point out that many of these actions were typical for the time. He conducted offensive wars against enemies, including those who refused to convert to Islam. 
Ownership of slaves
Muhammad is also criticised for owning, enslaving, selling and buying slaves. He also legalised marriage of one's slaves and to have sexual relations to them, regardless of consent Surah 4:24 . Again, this was common practice at the time. Muhammad also encouraged slaves to be freed. He also discouraged the forced prostitution of slaves and only allowed enslavement of people in specific circumstances.
Polygynous marriages, as practiced by Muhammad, are condemned in most industrialised countries. Muhammad's wife, Aisha, was very young when betrothed (6-7 years old) and when the marriage was consummated (9-10 years old). The Qur'an, written by/revealed to Muhammad stipulated that a man may have up to four wives Surah 4:3 . Muhammad's fifth wife, Zaynab, was the ex-wife of Muhammad's adopted son Zayd Surah 33:37 and was contrary to the practices at the time.
When founding a religion, one might aim for a higher calibre teachings than found the in Qur'an.
Gallery of depictions, including those published by Charlie Hebdo and Jyllands-Posten Muhammad