Pentagon planned for Iranian invasion in 2004

The emphasis of this Guardian report is that Britain took part in the Pentagon’s mock Iran invasion “…despite repeated claims by the foreign secretary, Jack Straw, that a military strike against Iran is inconceivable.” Regardless of what one might feel about more British toadyism, the more basic issue is the evidence this constitutes of Pentagon planning for the Iranian invasion beginning as soon as the ‘mission” was “accomplished” in neighboring Iraq. Or did they set their sights on both and plan the two wars in parallel, even earlier?