The structure of Old English poetry, with lines separated in two by a caesura, but bound back together by alliteration, was not solely the property of the Anglo-Saxons alone. This poetic form was followed by every old Germanic language that we have poetic texts for. Here's a little article on the common Germanic poetic tradition:

Old Germanic Poetry

I welcome questions, discussion, corrections, etc.

Oh, and I'm now working on an article on how the author of Beowulf in particular used this poetic form to heighten the effect of his story. (This is the article I really wanted to write, but I realized I probably ought to go over the basics first.) *s*