TMZ has obtained a signed declaration by Diddy, filed in Los Angeles County Superior Court. While some people are spinning what he said to mean that he's saying that Gerard Rechnitzer, the alleged victim, ran into his fist; when you read the declaration, what Combs says isn't unreasonable. Here's the Cliff Notes version and Diddy's declaration to the court (again, this is what Diddy claims, not my own words - I'm just summarizing them):

On February 25, 2007 at around 2:15 AM, he was leaving The Roosevelt Hotel in Hollywood. A woman approached him from behind, stopping him and trying to strike up a conversation with him, consisting of small talk and what his plans were for the remainder of the night.

He says that he told her that he was returning back to his hotel, as he had been out late enough. As he was talking with her, a man he identifies as Gerard Rechnitzer, reached the area where they were. He appeared "intoxicated and agitated". Rechnitzer yelled that the woman was his girlfriend, which she then confirmed.

Diddy had two security guards with him, one of which had placed himself between Rechnitzer and Combs and the woman. As Rechnitzer appeared to want to be closer to his girlfriend, Diddy told the security guard to allow him to do so.

However, Rechnitzer was still "aggitated and upset" and he began to move toward Diddy. "... without warning, he lunged at me." Out of instinct, Combs stuck out of his hands (the hand was open and not closed in a fist) to prevent himself from being harmed.

He says that any contact between him and Rechnitzer was caused by Rechnitzer's unexpected motion, triggering an automatic response of Diddy putting a hand up to stop him. "I did not punch, slap, push or in any manner physically pursue Mr. Rechnitzer." After noting that any contact would have been minor, he says that Rechnitzer "did not fall to the ground, and did not make any sound or cry."

Via HHE.