First he told his wife then his family and his closest friends. As the book mention that Muhammad is known as "The Trustworthy One", that's because people knew in his lifetime he never lies. Beside his personalities is so gentle and a his behaviour is worthy as role model.Â
For the people who knows Muhammad characters and people who think to move on from the situation, they must be believe or at least respect of him. But unfortunately, most of them was "jahil".
Muhammad first revelation from God is "Iqra!" (Read!). A command to read. Why read, not "worship me!"? because when people read or learn, they knew, and they will do.
As any inventors in every ages that came up with new idea and concept, what Muhammad said at that time must be hard to be accepted by the Mecca people who had harsh character, strong tradition.Â
Do you remember what happened to Galileo Galilei when he supported Copernicus that the centre of the universe is The Sun (heliocentric) not Earth (geocentric)? He was tried in Rome.
So does Muhammad, he preach to worship The Only One God, which is transcendent, and then to treat women better, to respect the parents, even what is good to eat and drink and how to behave. From the most essential point to the etiquette. Everything is contrary to what it was in Mecca. How do you think the response from the people of Mecca right there?
The infidel (i'm using infidel term, as written in the book) people treat him and his fellows badly. The infidel Quraisy tribe  in Mecca torture the muslim and force them to back to their pervious faith. Because of this pressure and malignant situation eventually Muhammad and his supporters moved out from Mecca to Medina. That's why the war happened, as a defensive reactions from the infidel who wanted to persecute the muslim, not as offensive actions as written in the book.
Wallahu alam bishawab.
