Karen Armstrong made this claim in a recent article and I was wondering about the truth in it.

My general impression is that Mohammed did indeed use diplomacy to gather enough tribal support to supplant the Quraysh, but it's hard for me to look at the growth in the caliphate after his death and say that violence and conquest wasn't a big part of it.

How true is this? If you were to try to find a charitable sense in which it was true, what would be it? (e.g. did the Muslims use violence to conquer but come up with policies that allowed easier integration instead of repression?)

Thanks

EDIT:Full context