a religion of peace, wouldn't require an army and would require weapons, which is exactly what Muhammad built, first in Medinia, and later in the rest of the Arabian peninsula. Peace wouldn't require being "armed", and go raiding caravans and supplies, which is exactly what Muhammad and his earliest followers did. Peace wouldn't require him returning back to Mecca with over 10,000 armed men, or go around punishing those towns or villages who didn't accept him as a prophet or accept his religion in the first place. Peace, wouldn't require Muhammad lead the attack against the Qurayza, executed the men who didn't converted, and then enslaved the women and children.
And what happened immediately Muhammad's death. There were fighting between two factions, over leadership succession, and let's not forget it was army/armies that attacked Syria, and then Persia.
What of Egypt, the Caucasus, India?
The caliphates and sultans got themselves more land, more wealth, more men for their armies, more war captives in which they could enlarge their harems, after each conquest or invasion.
Do you remember that Muslims could attack any nation, until they give up, and each could take a fifth in loots or plunders? you couldn't do that without weapons.
Do you seriously there was not a single sword drawn in Muhammad's lifetime or afterward that didn't invade those countries? Yeah, right, really peaceful.
Seriously, it is just another bout of self-denials that many Muslims are so famous for.