Ex bello tam tristi laeta repente pax cariores Sabinas viris ac parentibus et ante omnes Romulo ipsi fecit.
After such an unhappy war the happy peace suddenly made the Sabine (virgins) more dear to the men, to the parents and, most of all, to Romulus himself.
I'm taking it that the subject of this sentence is pax and the adverb repente qualifies the verb fecit at the end of the sentence....