"We have defeated them twice."
Translation:Vyhráli jsme nad nimi dvakrát.
I'm tempted to say that in this sentence "nad nimi" is a clitic. I haven't found any reference to prove it though! Often, there are words that may behave as clitics in one sentence and not in another. These two syllable personal pronouns are a perfect example. You can use them at the beginning of a sentence to emphasize as well. (Nad nimi jsme vyhráli dvakrát. Nad nimi jsme dvakrát vyhráli. Vyhráli jsme nad nimi dvakrát. Dvakrát jsme nad nimi vyhráli.)
I'll post here one link with types of words that like to be clitics, maybe you'll find it useful. Look at the bottom where there are the eclipses. The top half of innermost eclipse is always a clitic and moving outside the tendency to be a clitic is reduced.