Sperrle thought the RAF could be defeated "en passant". His personal strategy to attack ports and merchant shipping was overruled by Göring, ostensibly because the ports would be required for the invasion. Kesselring's contemporary notes indicate he thought air superiority could only be attained for a short time, since most airfields and factories in Britain were out of range. Sperrle and Kesselring miscalculated, or were misled by intelligence, into underestimating the number of fighter aircraft available to Fighter Command—they put the RAF total at 450 aircraft when the real figure was 750. Chronic intelligence failures on British production, defence systems and aircraft performance inhibited the German air operation throughout the battle. Joseph Schmid, the OKL's chief intelligence officer, was primarily responsible for providing inaccurate and distorted information to senior German air commanders encouraging enormous over-confidence.