"Ils sont de notre force."
they are of our force? if you said this in English nobody would know what the heck you were saying...
This doesn't mean anything at all in French. "They are as strong as us" would translate to "Ils sont aussi forts que nous".
I wonder if this sentence makes sense in French.
The first translation doesn't make sense in English. The second does make sense but seems pretty far removed from the actual French words that were given.
Would a natural French speaking person take They are of our strength to mean they have the same strength as us without having to think about it for a while?
I could see this being natural. In English, you might say "they are of our intelligence" instead of "they are as intelligent as us." In any case, if somebody did say that, you'd probably know what they meant right away.
They are equal to us is incorrect and they are of our force. You mean they are on our side?