A Marine Corps general led a fictional Iran against the US military—and won
A significant military exercise took place in 2002, involving Lt. Gen. Paul Van Riper leading a fictional Middle Eastern-inspired force.
This force was designed to mimic a country like Iran, and Van Riper's mission was to oppose the US military. The exercise, known as Millennium Challenge 2002, was a large-scale operation with 13,500 participants and multiple training sites. Van Riper's forces achieved notable success, sinking a carrier battle group in the first two days.
Further details about the exercise and its outcome are available from the source, including the response of US military brass to Van Riper's successes.