The US says the operation was a combat search-and-rescue mission to extract a downed F-15 pilot from Iranian territory. But a parallel theory - circulating among some commentators - suggests a covert ground operation may already have been underway near the Isfahan nuclear site before the jet was shot down. Proponents of this view argue the rescue may have exposed a larger mission, forcing a rapid extraction under heavy fire. Washington has so far stuck to its official version, declining comment on any covert activity.