More evidence:
"According to Muslim biographies, Muhammed, having received intelligence that Byzantine forces were concentrating in northern Arabia with alleged intentions of invading Arabia, led a Muslim army north to Tabouk in present-day northwestern Saudi Arabia, with the intention of pre-emptively engaging the Byzantine army; the news, however, proved to be false. Though it was not a battle in the typical sense, nevertheless the event represented the first Arab attack on the Byzantines. It did not, however, lead immediately to a military confrontation.[8]"
https://en.wikipedia.org/wiki/Arab–Byzantine_wars#Muslim_conquests.2C_634.E2.80.93718
He received intelligence that was false.
It was false but Muslims attacked the Byzantine empire anyway, and all of North Africa, and India, and Persia, and Europe (Spain, South-East-Europe, even France).
So was that all in defense?
I really want to hear your justification for Christians not being able to preach to Muslims. By the same standard, Muhammad should not have been allowed to preach to polytheists of his day.
You are in favor of oppression. You live in the UK. You can go to a Christian and tell him how great the Quran is and that he should convert. By your own standard you should not be able to do so because you live in a Muslim minority country.