A provocation, but by whom?

I wonder if this is the trigger for war with Iran:

DUBAI, United Arab Emirates - Iranian naval vessels on Friday seized 15 British sailors who had boarded a merchant ship in Iraqi waters of the Persian Gulf as part of efforts to protect the Iraqi coastline and its oil terminals, U.S. and British officials said.

My guess is that this actually happened in Iranian waters or at least in contested waters and not in waters that were incontestably Iraqi. The Iranians aren't stupid, and they certainly know that any overt act against us would lead to massive retaliation. Everyone would suffer, but they have to know they would suffer the most. They're not going to be the ones to start the war. (It's the same reason I don't play chicken with eighteen wheelers). And, who knows, maybe it was deliberately staged by us to create an international incident.