[rgcraig]

Yield:
3. to give up, as to superior power or authority: They yielded the fort to the enemy.
4. to give up or surrender (oneself): He yielded himself to temptation.
5. to give up or over; relinquish or resign: to yield the floor to the senator from Ohio.
6. to give as due or required: to yield obedience.

Surrender:
1. to yield (something) to the possession or power of another; deliver up possession of on demand or under duress: to surrender the fort to the enemy; to surrender the stolen goods to the police.
2. to give (oneself) up, as to the police.
3. to give (oneself) up to some influence, course, emotion, etc.: He surrendered himself to a life of hardship.
4. to give up, abandon, or relinquish (comfort, hope, etc.).

Are they really different? "to give up" seems to be the basic meaning of both.